Help for a New $500-$700 Gaming Rig

APPROXIMATE PURCHASE DATE: Very Near Future

BUDGET RANGE: $500-$700 (the lower the better)

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: GAMING, video editing, surfing the interwebs.

PARTS NOT REQUIRED: Keyboard, mouse, speakers, monitor, OS (Windows 7)

PREFERRED WEBSITE(S) FOR PARTS: Newegg

PARTS PREFERENCES: AMD (AM3 please), but im open for anything that has a better price : performance ratio.

OVERCLOCKING: Yes, i want the most bang for my buck.  

SLI OR CROSSFIRE: Possibly in the future.

MONITOR RESOLUTION: 1440x900

ADDITIONAL COMMENTS: i need this to be VERY upgradeable for when im not so tight on money, or when its the time of year to upgrade again. i want this case, so include it in price, but don't look for an alternate for me. Also, i want to be able to play these games on maxed settings: Crysis (Warhead), Call of Duty 4 and 5, TF2, and pretty much any other newer game i throw at this beast.