1x7950GX2 vs. 2x7900GTX vs. 1x8800GTX < Important!

my new build consists of a 7950GX2 card which is AMAZING, but i need some help.

next week im getting a DELL 30" Widescreen Monitor, and it is recommended for BEST performance to have a HIGH END SLI set up.

now, since 2x7950GX2 or 2x8800GT(S)(X) is out of the question, the next runner up is 2x7900GTX (and im not going crossfire here - my board is nForce4 for a reason - ASUS P5N32-SLI SE Deluxe).

how do they compare? reviews have given odd answers, mixed opinions and reactions and what. i need to know ultimately, crunching down to SHEAR GAMING AND MEDIA POWER -- and overall BEST performance with that monitor and other hardware in the computer (core 2 duo, that motherboard, 2GB ram) -- which is better -- 1x7950GX2, or 2x7900GTX.

now once that is determined: 256MB or 512MB? 512MB make enough of a difference?

either way i can trade my 7950GX2 for 2x7900GTX with very minimal cash added.

but im sure 1x8800GTX beats all this out...right?

please let me know folks. thanks a lot!

MERRY CHRISTMAS!!!