How many 2560x1600 resolution monitor can Eyefinity support? AMD states it can support up to 6 monitors but they don't state the resolution.
The ATI Eyefinity tech brief explicitly mentions this setup, so you should be good :) Just make sure you have enough displayport outputs.
And I can see your other SU questions have related to this, so here: the easiest way to get an absurdly high resolution running off 1 card is probably a 7870 with 6 dp outputs, like this one. Not that cheap for a gaming card, but very cheap compared to the pro stuff... and, actually, really cheap compared to the cost of 6 WQXGA monitors anyway. Or, for that matter, one WQXGA monitor.
And here are the possible layouts, screenshot of the Eyefinity setup page. (Oh, there's also a 5x1 vertical resolution that was just added, for 8000*2560 with these monitors, but it's not in the setup page yet.)
Edit: For a non-gamer (programmer, perhaps?), there isn't really an advantage to Eyefinity, and you don't have to worry about layout really, so you could actually put 6 monitors side-by-side if you wanted, or any other layout, just as separate monitors instead of a single hires display. But this is a bit out of the question scope.