PCIe 2.0 x16
SLI / Crossfire support
3 video outs.
Obviously the fastest possible.
What it will be doing:
Displaying on 3 monitors at once. (They are 1440x900, 500x900, and 1280x1024)
And I plan on doing a bit of gaming on the 1440x900 screen. (MineCraft, Portal, Rise of Nations, etc.)
None of those cards can output on three screens. You'll need an AMD card for that. (or an Nvidia card from the 6xx series.) That PSU also only has two plugs for video cards. This limits you to the GTX550TI from Nvidia, or the 7850 from AMD.
I've done a bit of SLI research, and am still a little fuzzy. If I have two 550Ti cards using SLI, can I use 3 monitors?
Could I use 3 monitors if I disabled SLI???
The GTX 550 ti has a quite high pixel rate among the cards in that price range, that's why it does not lose that much performance when running in high resolutions or using multi-monitors, so you should be fine with GTX 550 ti SLI'ed..........but if i were you i would go for the single 560 since it will perform slightly better than 2 of the GTX 550 ti and cheaper