I do professional video editing work myself, so I'm going to give you a suggestion. for professional video editing work, you should really be on at least a Nvidia Quadro CX or a AMD FirePro V7800 with any of the current 6-core cpu's. (1055T/1090T/980X) <-- in order of performance
At the other end of the scale I still edit HD video (HDV or DNxHD) on my Pentium-4 with a 7800GS card; it's far from ideal, but perfectly usable so long as you don't expect many realtime transition effects.
My vote would go for an i7 and a decent video card with plenty of RAM and lots and and lots of disk space.