Building and Upgrading Question

Hi,

I just build this early October 2007. Specs:

>> Q6600 Go Stepping
>> 8800 GTS 320mb Superclocked
>> Apevia mATX camouflage case w/ 500 W PSU
>> Kingston 2GB 800
>> Samsung SpinPoint T Series
>> Creative Sound Blaster X-Fi XtremeGamer
>> ASUS P5B-VM DO mATX
>> LG DVD-RW Lightscribe
>> 19" Wide AG Neovo
>> M518 Logitech
>> Logitech 5.1 speaker
>> Standard Keyboard

I spent less than $1500, maybe about $1450 (all on newegg/clubit/amazon).

So, I played F.E.A.R on this thing and set up all high setting just to test it. It blew on me. The screen practically froze   .I figured it's prob. the GPU problem. Then I tried BioShock and it looks pretty good (I think it's med settings). Haven't overclock anything yet because I'm running out of room for extra colling system. I know I should've got thermaltake LAN case (mATX), but it seems to be bigger than my current one (I'm petite, so I can't really lift it, which is the main point of mATX case, and I live in this small dorm).

Is there anything that all of you think I can do better in med budget gaming rig? should I go SLI next time (dual gpus sounds delicious to me)? I might want to build a gaming rig for my brother, do you think ATX is the way to go or stick with mATX? Back to my pc, sould I do raid 0/1, cos I can technically stick another hd in it?

Thanks for reading.