Trade some power for space, disc and desk top. Fast quad core is nice as render times can never be quick enough and if you get into using lots of complex tricks it's handy but not essential.

What you do need more of is storage, preferably secure storage. Considor a speedy raptor for sys and then a large safe raid array for storage.

Editing is much easier with lots of screens - go for 2.

GFx card is totally irrelevant for editing.