With the exception of moving in a few fans of daylilies, you will only have seasonal interest in the springtime.

I would think first about some 'bones' for the garden. Possibly a shrub or 2 or 3 at the back. The sun hydrangeas provide a very long season of color, but size does need to be taken into consideration. My Limelight Hydrangea in a bed soon grew huge, as did my Quick Fire Hydrangea.

Next you might consider other accoutrements....ie bird feeders, bird bath, maybe a bench, etc. Once those things were in place, along with other perennials, I would then give the bulbs count and placement consideration.

Were you maybe thinking of planting annuals then in it after all the spring blooms are gone and the foliage is fading?

Here is a related thread covering hiding what some consider bad looking fading foliage.
Best choice for planting over tulips?

Sue...chemocurl

You don't say which state you are in, but if you are in a warm more southern state(7b), don't count on many of the bulbs you mentioned being perennial. Before you invest alot of time, money and energy in a mass planting you might want to call your county Ag office and speak to a Master Gardener about which bulbs do best in your area. Tulips and Crocus for instance are not reliably perennial even in my 7A zone.

I'm with Sue, remember most of your bulbs will only look good in the spring and some of your selections may die out after a year or two.
As far as spacing goes, you could stuff 50 crocus in a square foot but maybe only 2 tulips will fill it.

If I were doing the flowery meadow look I'd go with daffodils, lilies and perennials such as feather reed grass and perovskia to fill the gaps. With more info on your location I'm sure we could quickly fill those 250 sq feet! ;)

Listen to maryl. If you live in the south, of your list, only the crocus are likely to be long lived, and that, only if you are planting tommies. If you want a bulb garden in the south, your first purchase should be "Garden Bulbs for the South" by Scott Ogden. It's a great book and you won't go wrong giving it a careful read and ordering accordingly. Bulbs are not cheap. If you buy first and fast, you'll regret it later.

Also, listen to chemocurl. Bulbs are great plants, but nearly all of them have bursts of beauty, followed by weeks of ragged, ratty looking foliage. They do far better planted among shrubs (preferably evergreens) and perennials. If you have a friend in your area who is an avid gardener, they can tell you what does well.

This being said, here are some of the bulbs I love best in my zone 7B/8 garden:

Spring:
Arum Italicum Pictum "Marmoratum" (this is really a winter bulb)
Narcissus, Grand Primo It began blooming at New Year's last year.
Narcissus, Avalanche
Narcissus, Campernelle
Narcissus, Trevithian
and many more daffodils.
Ipheion uniflorum, Rolf Fiedler
Leucojum
Hyacinthoides hispanica (Spanish Bluebells. Wonderful!)

Early Summer:
daylilies (not true bulbs, but often sold by bulb companies)
Gladiolus byzantinus "Cruentas"
Amaryllis

Mid to late Summer:
Cannas
Crinums: These bloom off and on throughout the summer. Below are recommended varieties.
Milk and Wine (You have to get these as pass alongs)
Elizabeth Traub
Stars & Stripes
Cecil Houdyshel
Mrs. James Hendry

Zephyranthes: Rain Lilies
candida is white and IMO, the best, but there are pinks and yellows too

Good bulb catalogs will tell you how many bulbs of a variety to plant per square foot. As Sue said, this varies widely. One crinum can cover six square feet when full grown. Ipheion, on the other hand would probably need 18 or so to fully cover one square foot.

If you get yourself some large sheets of white paper and do a 'sort of scale' outline of the two areas you're working with as a first move.

Then look out your windows and think about what you would like to see over the various seasons - perhaps this way:

the first ones - the earlies such as snowflakes and snowdrops and glory of the snow. The early Narcissus from whatever is hardy in your zone.

And what keeps them company - forget-me-nots and polyanthus and the early primulas. If you have unfriendly summers then you can treat the polyanthus as annuals. Calendula is also a vivid possibility, as are pansies.

Around them are the 'bare' patches where there are dormant plants, or various shrubs both deciduous and evergreen. (Both is better: one gives some form to the garden while the other provides interest over two to four seasons. Ones with interesting stem colour and form can be delightful in winter, for example.)

Then there's the Grand Display for spring - and that's when you need to think about colours and heights and flowering times. You also have some lovely leaves unfurling, such as some of the hardier japanese maples which can either clash unpleasantly or really lift your garden pictures into the sublime.

Just remember that it's a very fleeting event and the yards of green leaves hang around like a hay meadow for months, in some cases. I can tolerate that in the less public areas of my yard but I prefer to have other eyecatchers about while the leaves are feeding the bulbs below. Flowering plums and dwarf fruit trees, early Clematis, if that's seasonally possible, and the early perennials such as Astrantia, Heuchera, Euphorbia which give lasting colour and texture.

Then the later bulbs - remembering access to do any tieing to stakes you might need for Gladiolus and Dahlias or Dianthus.

Instead of mighty swathes think, perhaps, more of 'settings and backgrounds'. Little vignettes linked by colours and repetition because this is a public area and you are sharing your tastes with others.

If you want bulk quantities of bulbs for filling the vases and gifting - think of making an industrial growing area in the more private part of your yard - a cutting garden which can also double as a place to try out new varieties and hardiness and longevity before you put them on display.

And, as you plot and scheme on those sheets of paper - put in the access tracks for the inevitable lifting of over-large clumps, and soil feeding with barrow loads of compost, and deadheading. There are few things as attention-focusing as stepping on something beloved inadvertantly while dropping heavy tools on something else...

When you've got it all on paper - go out and check your reality.

From your planting diagram you can work out how many of what you will need. For such a large area think in terms of clumps of five as a minimum. Write the numbers under the plant names in the planting shapes on the paper - then create a list of numbers, species, and varieties - and -place your orders, please.

Have we overwhelmed you yet?

Regardless of what you decide to plant and where to plant it, just remember that beds (or gardens as some call them) evolve over time. I'm either planting, or rearranging, or planning changes all of the time.

Whatever you do choose to plant, will likely look good, but as time passes you will maybe see that moving things around a bit will look even better. True gardening is an ongoing experience.

Sue