Recently purchased a Gateway Slim Desktop SX2851-09e. Wanted to install a better graphics card but I am being told I need more power. Is there a larger powder supply..min. 300 watts that will fit in this Gateway. Or do I need to go to a lower video card that will only need 220 watts.... I'm trying to run a better card so I can run the DVI thru a Atlona DP400 out with MiniDisplay port to a Mac 27" MiniDisplay port in. Any help would be a appreciated.