Geforce 6800 Ultra vs Geforce 7800 GTX

I'm looking to buy a new video card for gaming, a top of the line
version. I've always stuck with Geforce over ATI so I guess I will do
that again. I am confused about the difference between 3 cards.. the
6800, the 6800 ultra, and the 7800 GTX. Can anyone give me some insight
or point me in the right direction? Which should I buy tomorrow?

TIA 10/19

 

Nvidia has two recent series of cards: 6x00 and 7x00.
In the 6x00 series there are several cards (actually, too many to
remember, because they keep giving them new names):
6200: The budget card
6200 TC: Budget card that uses TurboCache, a technique that uses your
system RAM.
6600: Sometimes the same core as the 6200, but these cards are the
better cores, because they are clocked higher. Often used in HTPC's
because they can be cooled without fans.
6600GT: Though it has the same name as the 6600GT, this one can be used
in SLI, has a different core and is a lot faster.
6800LE: The budget version of the 6800 core. Has only 8 pipelines and 4
vertex shaders when you buy it, but you can unlock 8 pipes and 2 shaders
more.
6800 (NU): This is one step higher from the 6800LE. It is actually
called 6800, but some people say NU because 6800 is also the name of
this whole series of cards
6800GS: It should be a little cheaper than the GT, but it should perform
about the same.
6800GT: Not as good as the ultra's, but the cheapest SLI ready 6800 card
(correct me if i'm wrong)
6800 Ultra: The best Nvidia card, until the 7x00 series came. SLI ready.

7800GT: The cheapest 7x00 card, and also SLI ready. These cards are
great for overclocking
7800GTX: This is the best card you can buy (perhaps just because you
can't buy XI800 yet). If you have to choose between the cards in the OP,
choose this one.

 

Highest numbered card wins, i.e. 7800GTX is fastest of the cards you
mentioned. More details / benchmarks...
http://graphics.tomshardware.com/

However, the newly released ATI Radeon X1800XTs are faster than the 7800GTX.