Best PCIE 1 graphics card?

I have an e5400 clocked at 3.5 ghz on a Biostar g31-m7 TE motherboard and I'm looking to purchase a new graphics card to replace my 7600GT. The only problem is that my motherboard supports only PCIE 1 and not PCIE 2.

According to the motherboard manual, the pcie slot on this motherboard is pcie_1.0a compliant, maxed theoretical bandwidth of 4gb simultaneously per direction, for an aggregate of 8gb/s totally and supports a raw bit rate of 2.5gb/s on the data pin.

Most moderate graphics cards seem to be pcie 2 these days. I know that they are backwards compatible but doesn't that come at the cost of reduced performance? And if so, how much of a reduction are we talking about here?

I was thinking of getting either the 4830 or the 4770 but if my pcie 1 is going to cripple the performance noticeably, I may just opt to get a new mobo/build.

My aim is to be able to play Far Cry 2, SC2, Diablo 3? on very high/max @ 1400x900.

Thanks for the quick reply

So you're saying that my mobo will not hold back a Radeon 4830 from full potential? I'm using 380W Antec, it's got a 6 pin pci-e connector and according to the power consumption charts, the 4830 doesn't take up too much juice so hopefully, that'll be enough...

Also, can you believe that I got both the e5400 and the mobo for 79.99!?!?! At first I thought that board would be utter crap because it's one of those freebie combo boards but it's actually turning out to be quite a good board. It's been very stable thus far for my overclocked build and I'm not even using the suggested 1.8v rated RAM, rather I'm using 2.0v rated, overclocked at 960mhz and it's still okay! The only downside I thought would be the pcie 1 but I guess that's okay too!

I don't think the 40nm is worth it personally. The 4830 is still better than the 4770 in terms of performance per dollar AND performance per watt according to the charts coozie linked to so I don't see the reason to pay more when the 4830 will get me the performance that I'll need at the resolution I want.

Well, I guess if I see a 4770 at $90, I'll have to pick it up since I've been reading other review sites and they say the 4770 is better than the 4850 when OC'd while consuming less power to boot.