Go the Core i7 route.  Last Feb I didn't pay attention to Pinnacle's stating a quad core at 2.66Ghz minimum was required to edit 1920x1080 17Mbps AVCHD and I ordered a Dell with the Q6600 quad core at 2.4Ghz.  I had constant frustrations trying to work with the highest resolution video the Canon HF100 had.

A graphics card swap to an Nvidia 8800GT 512MB card helped but editing was still sluggish.  I've had a Core i7 for several months now and editing goes smooth.  Irony is, the Core i7 machine from Dell with a 22" monitor cost no more than the the Q6600 machine from Dell.