Even if your motherboard is only PCI-E 1.0 or 1.1, 2.0 cards are backwards compatible, and will be hampered in performance by only a very very small amount, especially in the price range you are interested in.
I am not familiar with UK retailers or prices enough to suggest a specific card, to be honest, but ATI 4870 or GTS260 would probably be a good starting point in finding a big increase in performance.
someone on another board said i shouldn't put an ATI card on a 680i
is that true? and if so why?
they also said i should get a DX11 card? (i know DX limits compatability and older cards can't support newer versions but how bad is it really?)
i had a look at old 8800GTs but mine came factory overclocked and most of the cards on UK ebay are over £60 ($90) also i need a card to use in a secondary system so that'd be £30 if i dont replcae the 8800GT
only reason not to get a ATI card on a nvidia chipset is like getting a Nvidia card on a AMD high end chipset because the Nvidia chipset only supports SLI while the high end AMD chipset only support Crossfire
Basically it seems like a waste to have a mobo that can crossfire or SLI and have a card that can't
Other then that there should be no problem.
Easy way to ask if you should go for DX11 card.
Do you have windows 7 or Vista
if not then when will you?
if it's not going to be soon like 6 months a year then why bother getting a card that supports it when your OS does not.
I still think another 8800gt for now would be your best bet, for multiple reasons. Cheap (less than $80USD), 2 in SLi will outperform a gtx 280, 4870 and possible other cards in the category. down the road you can upgrade to dx11 if all your into is gaming.
Two 8800GTs is not roughly equal to GTX 280 performance. Two 8800GTX 512MB is about equal to GTX 280 (NOT a GTX 285). Two 8 or 9800GT is roughly equal to a GTX 260 216sp if they're both 1GB. If they're 512MB it's roughly equal to a 9800GX2 which is around a stock GTX 260 192sp (probably a bit lower). Adding another is a decent decision if they're both 1GB. If not, and they're 512MB, just get an HD 4870 or GTX 260 216sp.