what I posted is absolute overkill for gaming and for making videos. the two hardest things a computer can do for normal users.

Realistically you might want an i5 or a lower end i7 with a 5870 and 6gigs of ddr3 in triple channel
A mid sized tower and a an 800 watt PSU to give you space to upgrade to crossfire 5870

Or if your budget is even smaller go with a phenom II.