Hi im upgrading my pc soon and i have a few question 
at the moment i have:
Mobo: Asus k5n-sli
CPU: AMD x64 3700+
Gcard: Point Of View Gforce 8800GTX 320mb
Ram GeIL 2GB (2x1GB) PC2-6400C4
What im going to buy:
Mobo: Asus P5N-E SLi nForce 650 (Socket 775) PCI-Express DDR2
CPU: Intel Core 2 Quad Pro Q6600 2.40GHz Guaranteed to run at 3.00GHZ (1333FSB) - Retail
Gcard: NOT SURE YET, QUESTION BELOW
Ram: Another GeIL 2GB (2x1GB) PC2-6400C4 to make 4gb
My question is with the graphics card.
Should i get another 8800GTS and sli with the one i already have or should i buy: OcUK GeForce 9800 GT 512MB
also if i was to buy another 8800 would it have to be 320mb like my other one or could i get a 512mb one and still sli with my old one?
thanks

at the moment i have:
Mobo: Asus k5n-sli
CPU: AMD x64 3700+
Gcard: Point Of View Gforce 8800GTX 320mb
Ram GeIL 2GB (2x1GB) PC2-6400C4
What im going to buy:
Mobo: Asus P5N-E SLi nForce 650 (Socket 775) PCI-Express DDR2
CPU: Intel Core 2 Quad Pro Q6600 2.40GHz Guaranteed to run at 3.00GHZ (1333FSB) - Retail
Gcard: NOT SURE YET, QUESTION BELOW
Ram: Another GeIL 2GB (2x1GB) PC2-6400C4 to make 4gb
My question is with the graphics card.
Should i get another 8800GTS and sli with the one i already have or should i buy: OcUK GeForce 9800 GT 512MB
also if i was to buy another 8800 would it have to be 320mb like my other one or could i get a 512mb one and still sli with my old one?
thanks