2 x23" Ultrasharps are looking really good right now! I am leaning in that direction. Thankfully I have some wiggle in the budget but I don't want to spend for spendings sake.
My vote: two 24" monitors. I've been using dual displays for a long time. I just recently had to retire my 7 year old 23" ACD that I used alongside my new 24" LED. I researched a lot before deciding on replacements and based on what I read I went with two Dell U2410's to flank my 24" Apple LED. The Apple display was a little less than two Dell's, so I thought I was making a good move. However, no matter how hard I tried I could not calibrate the Dell's to the Apple display OR each other, using both software and hardware tools. In addition, both Dell's had bad pixels. I read more on Dell monitors, and generally speaking they suffer from banding issues to dead pixels to uneven tinting (both my Dell's had green to pink tinting cross screen).
Honestly, having used Mac's for years, the work perfectly out of the box with Apple systems. When working in print/photography/etc. you need a great system that is calibrated, which means you most likely need third party equipment that isn't considered when buying non-Apple displays.
My point, strongly re-consider the Apple 24" units. I returned both Dell's and got a full refund for $1k, and was able to purchase two 24" displays for $599 on the refurb store. No problems, and unlike what some say, no glare issues, just a great, crisp yet smooth and bright display that doesn't need calibration.
PS I've read that Dell uses the same panels as Apple displays, LG panels. However, unbelievably I have read in many instances, that Apple gets the pick of the best, and other companies/contractees receive the rest. I find this to be untrue as I can't believe this would occur, however doing more research I have learned that Dell displays generally experience more issues than Apple displays. I know that some iMac's had yellowing, but when you consider that LG supplies the panels for their iMac's, one of the top selling systems, and their displays, given the numbers, I'd still stand by Apple's quality.