Thanks guys. The reason why I'm so twitchy about video memory is that I upgraded to a 1680x1050 TFT LCD from a 1024x768 CRT last spring, and immediately noticed enormous performance sags. My current 8600GTS (from the comp I just built) is...underpowered. In my ever so humble opinion, it was a total waste of money. I'm not even going to try SLI'ing two of them, just gonna cut my losses and go 88xx series.
And on the new cards...I totally doubt I will have the money for a quad or any of the uber-new cards, and I will venture to say that 8800 ATX and Ultras won't become affordable. They'll drop down to the high-end GTS 640MB area ($300+), and the new cards will be priced even more ridiculously.
Or maybe game developers will regain their senses and start making games that the average gaming rig can easily run.
EDIT: After further research (and your thoughtful advice), I think I might be leaning towards an EVGA 8800 GT SSC 512MB. First, it seems that the XFX 8800 GT XXX has yet to arrive. Second, since I got my 8600 GTS less than 90 days ago through TigerDirect, and still have all the boxes, packaging, etc, I do believe I qualify for EVGA's Step-Up program. At $300 or so, the 8800 GT SSC seems to be a decent buy, and is impossible to pass up if I do qualify for the Step-Up program. Anyone use Step-Up or have experience with that particular card? It looks fast, seems to get solid reviews, and appears to get some pretty damn good framerates and benchmark scores on games I might care about (Call of Duty 4, namely).