there are lots of ways to achieve this...I suggest going to a good molding store and working with the guys there to 'create' a profile that you like from their pieces there. A good place near me has 6 inch samples that you can take home and check in situ.
For that depth of molding, I used a simple L shape to start and attach to the top of the cabs, then a thin crown profile, a 6 board then a 4 inche crown at top. This created height without being too fussy or expensive as much of the height is taken up by a 6" flat board.
caspian

Our ceilings are also 9 foot. We did 4" furring strip and a 5" crown. Looks like this:

Caspian, thanks for the tips. So does that mean you used 3 pieces? an L shaped piece, then a 4 inch crown piece and then a 6 inch board? I am wondering if I can skip the L shaped piece since it sits behind the other pieces?

Taggie, thanks for the pics. Did you also add an extra decorative rope piece at the bottom of the 5 inch crown piece (or is that what you mean by 4 inch furring strip, sorry i don't know what a furring strip is..)?

Also, I am wondering if there will be a line/gap that shows where you put the two pieces together so that you need to cover it with a small molding piece like the rope molding?

Sorry michoumonster, I might have the terms wrong. By furring strip I meant the flat piece below the crown ... the rope molding is attached about 2/3 of the way up the 'furring strip' or whatevertheheck it's called. :) So the crown starts approx an inch above the rope. Hopefully that makes sense.

With 9' ceilings and 42" cabinets, you will need 12" of moldings, not 10". Top alignment height of 42" cabinets is 96". 12" is too tall proportionately, even for 42" cabinets. You need either 45" cabinets and 9" of moldings or 48" cabinets and 6" of molding. Or stacked cabinets, with 15"s on top of 30"s.

If I'm not doing stacked, I usually use 45" cabinets, a horizontal shaped profile piece to come out to the door depth, a 6" flat stock piece, and tall classic crown molding, perhaps with some library molding on top of the 6" flat stock for more detail if desired.

Ah I see. Thanks for the clarification Taggie! So the rope is purely decorative and isn't needed to hide any seams. I see now how you put the crown slightly forward of the 4 inch base to avoid seams. thanks again! I enjoy seeing the pics of your beautiful kitchen.

Livewireoak, I was thinking if I hang the uppers at 20" or 21" above the 36" base cabinets, then the 42" wall cabs, I would need 9 or 10 inches of molding. With a 2 inch light rail below the cabinets, I would get the standard 18" backsplash space in between uppers and lowers, that is, if I did the math right..
But sounds like 45 inch cabinets with shorter moldings would be nicer since you get more storage and not look as disproportionate? thank you for the info!

With 42", all of the cabinets use the same 96" horizontal line around the room as the top alignment height. If you are using an over the refrigerator cabinet, it won't line up if you shove the other cabinets up 2" above the alignment height. Neither will the oven or pantry cabinets, which will only be 96" tall.

Our cabs are 20" above the counters for the same reasons you state. 18" with the light rail would be too tight, imo. Our cabs were custom so it wasn't an issue getting fridge cabs built to line up.

If you're going stock, couldn't you do 21" above countertop and have a 3" shorter fridge cab to line up at top? I'd personally rather have the cabs at 21" than 18" if there's a 2" light rail.

live_wire_oak, thanks for explaining. i didn't think about the alignment issues with stock cabinets. I was toying with going custom-- this may be a good case for it now. I got a built-in refrigerator on closeout, so I have to figure out how to do the cabinetry for it too. I didn't research this yet, I am not sure if you can put cabinets above a built-in fridge?

taggie, thanks for your feedback. I can go with a 1 inch or 1.5 inch light rail. I do like having more space underneath to put things like a blender. I also got a tall semi-pro faucet that will probably look better if I hang the cabinets a little higher above it too.

Michoumonster - I have 9' ceilings. I did 42" cabinets on one wall which do not meeting the ceiling, and on the other wall I did stacked cabinets which meet the ceiling. I really liked the stacked cabinets. Not only do they provide extra storage, but with them, it meant I didn't need a big molding. My molding is about 3", for both the 42" cabinets and the stacked cabinets that meet the ceiling. My cabinets are semi-custom, and when I discussed the various options with the cabinet guy, I decided against big moldings because (A) they were very expensive, so that stacked cabinets wasn't much of a difference in cost, (B) at that expense, the moldings were using up space but not providing utility, and (C) I found big moldings to be too fussy for my kitchen's decor. These are just MHO's, but I thought I'd give my $.02 (for what it's worth!).

akchicago, thanks for your input! i think all of your assessments would apply to my kitchen needs too. I prefer the stacked look too, moreso than a single tall cabinet. My only question is, with your stacked cabinets, do you need to cover the seam where they are stacked? I guess from the front, the doors cover the seam, but maybe on the sides does there need to be something covering it?

Michoumonster, my cabinets are frameless, and as you said, any seam is covered by the doors (see Taggie's photo above). As to the sides, I think you mean the ends of the cabinet run, correct? One end of my cabinets is against the wall, so not visible. The other end is visible, but it is covered by an end panel, which is standard for cabinets. Your cabinet supplier should supply an end panel as part of the design. A sidenote - some people get end panels with frames or raised panels to match their cabinet doors. I opted for a plain smooth end panel. I wanted the end of the run to look like the end of the run, but others want an end panel to look like their cabinet doors. Just personal choice, but it will be yet another decision for you to make!

akchicago, thanks for the info on the end panels. yes, yet another decision to make.