AE7 (from what I understand) doesn’t not support dual processor setups, so if you’re trying to save some $$ skip the dual core for now, mut make sure your mother board would support one for future expansion.
Now.
If you really want the best bang for your buck, DO NOT BUY A PRE BUILT COMPUTER like from Dell, Apple, etc…build it yourself. I built mine, and at the time is was better than a top of the line Dell, and comperable to a top of the line Apple G5 (although Apple doesn’t offer some of the really cool setups you can do with a PC) for like a fraction of the price.
For hard drives, one thing you may consider is setting up a RAID array…instead of splurging on one giant hard drive, buy two smaller (cheaper) drives and set them up to work together (there are plenty of instructions on the net on how to do this). There are several ways to hook up a RAID array, but the way I did it (and I believe it’s called ‘striping’), basically a file is divided in half and each half is written to a respective drive. Ignoreing a couple other variables, you can essentially load and save video twice as fast this way.
With the new ATA connectors, which I think push like 3 gigs/sec, you’d be moving files at almost 6 gigs/sec (Again, ignoreing other variables in your system).