WHOA at them offering an upgrade that doesn't fit in the case? I think your mobo can have up to 16GB RAM with 4GB x 4 sticks config, so you wouldn't be maxed out with the 4GB RAM upgrade. Have you ever considered the possibility of building your own? It seems to me like they charge the normal Antec gaming case and PSU prices when you upgrade through this site, no disccounts are offered on them despite the fact that upgrading means you won't be getting the default case and PSU.. Just a thought..
Core 2 Quad Q6600 2.4GHz, CORSAIR DOMINATOR 4GB (2 x 2GB) DDR2 1066 (PC2 8500), SAPPHIRE Radeon HD 4850, GIGABYTE GA-EP45-UD3P ATX, PC Power & Cooling S61EPS 610W, Western Digital Caviar Black 1TB HDDs, LG 22X SATA DVD Burner with LightScrib, Winodows 7 Professional x64, Antec 900 Case