I wouldn't get anything in the 9000 series as they are a slight increase from the 8800 series. You will see an increase in performance, especially as you are using the older g92 320MB GTS, but to me it's not worth the price.
Your best bet is to wait until the new cards come out, that way all the better cards not will drop in price. There are also Ati cards that are around the same price and is better than the cards you listed. One of them being the 4770.
yeah the difference wont be big enough to justify buying a new card. if ur selling ur old card then u could go for it i guess... but u should put that down for a GTX 260 or a 275. they are pretty cheap tehse days.
The 9800gtx was similar or just ahead in certain scenaios than the 8800gtx, as the 9800 was simple a suped up 8800gts 512.
The 8800GTX beat the 9800 in some games using a larger res, with higher textures
I'm with Snowbum. The 9800GTX+ is far superior to the 320MB 8800GTS and is worth the upgrade if budget doesn't allow a GTX260 / HD 4870. At the right settings, you could easily see twice the performance going from your card to the 9800GTX+. If that's 25 vs 50 fps, at the settings you want to play at, that's huge. Just do your research and understand what to expect from the new card. What res are you gaming at? What games are you looking to play? FSAA important?
I don't like paying $90-100 for a refurb though when the GTS 250 has been around $100 new at times. Look for a new HD 4850 for about the same price new.
The 9800 GTX+ would not be worth the upgrade, especially if you plan on eventually moving up to an 22 or 24 in monitor. I upgraded from the 8800 GTS 320MB to a 9800 GT but wasn't so I got the 8800 GTS 512MB, wasn't happy so I got the GTS 250, wasn't happy so I got the GTX 260 and finally happy!
Sell your 8800 GTS 320MB to a friend for around $50 or less, then add the cash to your budget and you'll have enough for the GTX 260.
I was thinking the ati because im a amd fanboy but i was wondering if my cpu will be bottle necking performance i purchased a oem machine and it came with a intel conroe e2220 @ 2.20 ghz. also runig 4 gbs of corsair and a apevia 500 watt psu on a 32 bit system