Here's my rig quad 24" Dells hooked to Nvidia Quadro FX570 Dell T3400 E8200 Core2Duo 2.66Ghz 4Gig Ram 525W power supply
I'm almost ashamed to post mine. One monitor. Horrors! But its all I really need (i've also got a laptop that sits to the left of the monitor, but its at a friend's house temporarily). I used to have a bunch (4) of monitors, but slowly got rid of them. My neck was really starting to hurt. LOL. All I trade now is the YM so this is sufficient for my needs. KISS and all that...
Well I think any computer will do for single monitor setups, but if your gonna have multiple monitors/video cards you need a computer that can handle the power output and I chose the the T3400 with the beefed up power supply, I would have gone up a notch if the power supply wasn't offered so I chose the lower level 3400 as I thought it would be fine for my needs. I priced the Dell against some of the specialized "trading computers" and thought I could save a significant amount by going with a dell. Oh, BTW the OP with the single monitor and nice and tidy desk, I'm jealous of how neat your desk is. I'm gonna work on that in the future.
Depends on what sort of graphics card you have. Something like Nvidia NVS 280/285/290 will be fine in just about any machine for up to 6 monitors or so, 'cause they are low power. Also fanless, so quieter.
That is my exact same setup at home -- 4 22s but on a black wood desk....at the office I have the same thing also but 4 24s on a brown wood desk. I love samsung monitors..IMO they are the best.