Help with upgrading graphics card in an Dell 8400

Okay, after spending alot of time researching this on the net and forums, im still having quite an time with deciding on an better card. First off here is my setup:

Dell Dimension 8400
Windows XP Pro SP3
3.4 ghz P4
2 gigs DDr2 RAM
Intel 925X chipset
Nvidia 6800 256 mb PCI express X16 (1.0)
350 watt PSU/dual rails @ 28 A - here is an link: http://www.ayagroup.com/images/C4849_1.JPG

I know my system is 5yrs old and limiting myself on the PSU and processor without any question, but I just want something a bit better than the 6800 to enjoy gaming with decent framerates without upgrading the PSU. Ive read almost everywhere that PCI 2.0 is backwards compatible with 1.0, but I ran across a few sites like this one that say otherwise on Nvidia based cards paired with my chipset:

http://www.xbitlabs.com/news/mainb [...] s_2_0.html


Also, after reading the current article "How much RAM does your graphics card really need", it seems like a card with 512mb of memory would be sufficient; while anything in the 1gb range wouldnt since Im running an 19in monitor and cant really achieve any resolution higher than 1680x1050, as stated in the article.

So, any suggestions on an newer Nvidia card, such as the 8 or 9 series?

I have the same system (an 8400 Dell) and have an GeForce 8800 GTS 512MB card in there and it runs just fine. Can Oblivion at max. Something from the 9600 line with its smaller die and lower power consumption should be fine.