Ya i7 will be a big improvement for me. I do alot of winrar, quickpar, and video conversions.
I am currently running e8400 @4.05 4G DDR2 ram @900 2x WD 640 blue in raid 0, ATI 467, windows Vista Ultimate. I'm gonna give this one to my 8 year old son, and keep the i7 for home, and use for a server for video to two more HTPCs around the house.