If you are looking at DV editing, then choose your platform based on software you'd like to use. Basically any standard PC will be fine for basic capture and editing. Pay more for a faster processor to speed up rendering, and a bigger hard drive for capture - thats about it. Oh, and a DVD burner. Twin monitors or a TV out might be worth looking at depending on which software you use. Real estate is always useful.
3-4 years ago you'd worry about HDD throughput etc, but these days the minimum requirement has long since been surpassed, so no real need to worry.
Its still worthwhile having a separate HDD for capture/edit, purely from a practicality point of view - much easier to back up if you want, and erase/defrag when you are done and ready for your next project.