8800 GTS question and resolution issues

So, I've been WAY out of the loop of how hardware's progressed in the last 2 years. (College time sucks ftl) I have an 8800 GTS 320 and I'm wondering if the new mid-range 9 series and 4k Radeons are an upgrade at all. It's kind of hard to find a comparison review between hardware that's 2 generations apart. If it's not a worthy upgrade, I'm throwing money to replace this weak CPU.

Also, I was playing TF2 last night and after a fresh reinstall of the game, it defaulted my settings to 1280x800 res. I was surprised when I noticed extreme choppiness whenever shots went off. I decided to get wily and bump it to the native resolution of my monitor, 1440x900. The lag was GONE for the most part. (I need to figure out how to combat the WinRot I have going on to fix that part.) Now, I'm not looking a gift horse in the mouth, but I'm just curious as to why a framerates would increase along with resolution. I've always thought of these as inversely related, especially if I only have 320mb of vRAM.

Thanks for the help!

I upgraded from a BFG 8800 GTS 320MB to a 9800 GTX OC2, played a massive difference in games for me. However be aware of PCI express 2.0 cards. the 965P DS3 has a bug which locks them in x1 rather than x16. Seems the "fully backwards compatible" isn't always true! lol Sometimes you can fix this, sometimes you can't! i was lucky!

also i would think about upgrading mobo, the 965P chipset isn't upta much anymore. Prob best to save ta cash up and splash out!

Hope this helps!

I went from a 8800GTS 320MB to a 8800GT 512MB and it was a night and day difference, any newer card should kill your 320MB so long as it is a ATi 4850/nVidia 9800GT or above.