Originally Posted by The Thing
It Will Work, But is pointless to get A extreamly high end card considering that the bus speed will not allow you to get your full potential out of the video card. If i remember correctly anything past the 8500 series would not get the full potential, but u can always go larger card, and eventually get new pc, but again, Deffinitly Check the specs of the psu and Probly Upgrade it to at least a 500 or 600 watt. Dont feel bad about the questions, as i too still ask alot, the idiot is the one who tries with out asking, the one who askes does once, and save's time and $$$.
I'd have to agree with you partially on your post. You are forgetting that the 8800GTX (still VERY NEAR top of the line) is only a PCIe 1.1 x16 card. Now if the new cards were for example PCIe 2.0 x32 (instead of x16), then yes, it would downgrade performance to use a 1.1 slot (x16 tops). But seeing as the cards are still only x16 bandwidth, there's no harm in it.
To the OP:
I would like to make note however, that your single core CPU, 1GB of RAM, and low end power supply would really be a bad idea with a newer GPU.
If you're looking for a new graphics card for your sig rig, I would personally go no higher than maybe an 8600GTS or 8800GS...and even the 8800GS would be pushing it with single core I'd think.