Whats better? 7800GTX or a 7900GT or GS?

[KnownKiller]

Trying to build my God son a computer for christmas on a budget and i'm trying to decide between these cards new or used ofcourse:

7800GTX
7900GT
7900GS

Isint one 7900GT faster then 2 7800GTX cards in SLI?

[crimedog]

7900gt is the best out of the three, and it overclocks like a madman :)

[jivetrky]

7900GT is the best out of the three. There's also a 7900GTO which is even better, but doesn't seem as easy to find these days. It is almost literally a 7900GTX underclocked.

And in some cases the 7900GT IS faster than 7800GTX's in SLI. Here's one review that shows a wide range of cards:
http://www.xbitlabs.com/articles/video/display/geforce7900gt.html

[KnownKiller]

OK thanks guy!