@ jixz, "Where did you get the gts is better than the gtx? the charts don't say that and logic will tell you gt gts gtx ( not taking in OCing )."
Depends on game, resolution and settings how the GTX, GT512 and Ultra are ranked. You're looking at SLI, so no chioce there, it is GTX.
@ Evilonigiri, your statement is reflected locally (Australia) where GTX and Ultra have had very low stock levels combined with only a slightly higher demand during November and December 2007, but still maintained their pricing when GT256/512s finally arrived and their subsequent demand (pre-orders only).
Even now with GTS256/512 cards available at wholesale and not by pre-ordering, the GTX and Ultra have not fallen in price.
As the GTX/Ultra approach their end of production by most , local importers and distributors will not putting their capital into a product that is likely to be superseded in every way. This has already happened with the GTS640 and then the GTS320, which maintained best buy status for sometime, but both have been dealt a death blow by the GTS256/512. Not in price, just in distributors stocking the product.
Price of the GTS320 remains unchanged from some distributors, but you might get yourself a flash drive for free when you buy a few.
Price of the GTS640 remains unchanged, but you've got to look hard to find quantities (not that anyone would).
Price of the GTX/Ultra are very unlikely to drop here (as you indcated), quite likely they will stay the same price indefinately, and a very slim probability they will go up significantly.
@ jixz (again), your market may be reacting very different to mine based on it's own supply : demand dynamics, and price drops may be imminent for some components.
However, if you were to buy 2 x GTS512s (SLI) now or 1-2 X Next Gen cards in February, and sell the current GTX, would this be a better outcome for you?
Lastly, more memory is always a good choice for most, 4GB total is nice, but there is no price reason to do this, only a performance reason. I would buy the extra 2-4GB yesterday, today or tomorrow.