I look forward to seeing the photos.
To keep a cohesive look I would recommend repeating the color of the foliage or flower on both sides. For example if you have lets say, yellow daylilies on one side I'd use yellow roses on the other side. Shape is also a good equalizer.

If you use some trees and broadleave evergreens like Azalea or Rhodies for structure and a backdrop, then you can have all kinds of eccletic stuff up front.

I don't think Rhodies and most azaleas would be happy in full afternoon sun.
I would add some trees for shade to the front yard if possible that would benefit both the plants and your energy bills!-

Why don't you take your collection of exotic plants and interplant them with some more common plant that you like? For instance, let's say you like the common dwarf indian hawthorne. You can plant drifts (be sure you plant in drifts with your exotic plants instead of one right after another) of your exotic plants in/around the more common hawthornes. One the other side of your yard, use the hawthorne, perhaps not predominately, but perhaps more occasionally. That would allow your exotics to shine against a background of the more common, and yet have a common tie to your other side.
I would suggest that you have a plan before you start planting. I think this is the most important step for your success.

Rosered,
I live in Aiken county, SC.
I have to garden in sand also.
It's all about symetry.
Go outside and take a pic of the house from the street.
Then print the pic on your computer.
Draw in as good as you can the approx size of everything you want to plant.
If you have a tree on one side, plant a tree on the other.
If you want a kidney shaped planting bed on the right side, put one on the other side also.
Try to make them match by shape of bed, size of shrub and trees.
You can draw them in the pic and see what you think.
It doesn't have to be perfect, after all, you will probably want to change it slightly over the years.
Good Luck to you!

You haven't said the house is symmetrical, and even if it is you don't need symmetry but rather balance.

I'm not clear on why you've chosen to divide the yard into "designed" and a "plant collector's" halves. You can design with special plants, integrating the two objectives. And you wouldn't be the first one to begin your design process with the plants you have or want. But what does catch my attention is the word "perennials". It may have escaped your attention that there are a lot of very special plants to collect in families like conifer, Japanese maple, and rhododendron ( you may curse me when you find out how much money can be spent on those plants :-)). I frequently recommend that people take a spin around the conifer forum to get an idea of the world of dwarf conifers. I started with perennials too, but am finding them much less gratifying and less amenable to being designed with as my interest in overall landscape has escalated.

What you're after with plants like that is "bones", which is something you can do with hardscape as well.

To post a photo, you could check out the gallery side, and put a link to it here in this thread, or you post from a Photobucket or other photohosting site. What you want to put into the body of your message here is the html code, starting with something like KarinL

I agree with karinl's comment about not dividing the garden and instead working on the "bones".

Consider what background plants would help show off your collected plants. It's an old trick to use a good basic evergreen workhorse behind a flashy but insubstantial or ephemeral bloomer. This is like selecting just the right shade of paint for your bedroom, or hanging a dark velvet curtain behind a person for a portrait. It's not the focal point, but it provides a flattering setting for the furniture or the face.