First Build, Help Needed

Hey guys, looking to make my first build. Won't be just for games, but it will be for games also, so quad core and a nice graphics card is a must. So far, I have...

Don't Need: Monitor (have an old Viewsonic), keyboard, mouse, sound card, speakers

GPU: Geforce 275
http://www.newegg.com/Product/Prod [...] 6814130479

CPU: Intel i7 920
http://www.newegg.com/Product/Prod [...] 6819115202

PSU: CORSAIR CMPSU-650TX 650W
http://www.newegg.com/Product/Prod [...] 6817139005

HDD: Western Digital Black 640 GB 7200 RPM
http://www.newegg.com/Product/Prod [...] 6822136319

Mobo: Not Sure...

Case: Not Sure...

RAM: OCZ Gold DDR3 3x2GB
http://www.newegg.com/Product/Prod [...] 6820227365

I'll be using this rig for gaming so I don't want to lag (will be trying Mortal Online probably) and video editing.
How does the build look so far? Any suggestions for a case and mobo? Think I should go with a bigger PSU?

Thanks for your help

EDIT

Will be overclocking! So fan help could also be helpful.

Monitor resolution will 1920x1200
The budget is roughly $1200
I will be hoping to run SLI or crossfire in the future when I can afford a second card.

swap the GTX 275 for an ati 4890, it's ~$50 cheaper and performs just as well if not better.

the PSU is fine.

get a P6T motherboard, anything above that isn't worth it for your needs.

for a case, get an antec 300 and a couple of 120mm fans or a coolermaster 690 and a couple of 120mm fans.

Would the ati 4890 really trump the GTX 275 in most cases? I have heard a dizzying amount of chatter on both sides of that argument.