i5-2500 or i7-2600 and 16GB of RAM (if you go prebuilt, get minimum RAM and add your own later to save $100 or more). Large 7200 RPM drive to hold video. Decent (But not high end gamer) video card for smooth HD playback. The rest is up to you.
Most of the "hassle" with editing DSLR video is that it comes in a file format that is less common (h.264 in .MOV wrapper). It's not really a hardware thing.
Originally Posted by ben_r_
like youre looking to buy a pre-built, which is never a good route to go IMO.
Never? You might argue that custom builds are a bit more flexible, but arguing that it is never good to go with a prebuilt is quite a stretch.