ATI X1950XT's are also quite a bit shorter & the Sapphire OEM version can be had currently on Newegg for
$244 with a $30 mail-in rebate
The cheapest 8800GTS is currently the EVGA retail model for
$389 with a $30 mail in rebate
Frankly given the disgraceful state of Nvidia's 8800 drivers (Both XP & Vista) if I had it to do again (I bought an EVGA 8800GTX) I would save my money & buy the X1950XT as a stop-gap, then wait & see what happens with the R600 & 8800 refresh models ... have no concerns about the lack of 512mb's VRAM on the XT, theres no card in its price range that can touch its performance & with the exception of being a bit loud really has no downsides.
The one other thing to consider however (& this is really the best idea) is to "suffer" with your 7800GTX just a little longer & see how things shake out with the next refresh ... either of the cards I mentioned at the top of my post will outperform what you have now by a good bit (especially the GTS... in between BSOD's), but I think the best place for your GPU fund right now is safely tucked in your wallet!
