Vista does a pretty good job balancing across the cores but most of the apps listed are not intensive at all minus the game. Instead of two idle cores you have four. I have very similair uses as you and mine stays idle a large portion of the time. I do a pretty good amount of encoding is why I went with the quad.
I would stay away from the F1. I have heard way to many reports of them going bad, the 750GB model in particular.
If you do decide to go with a dual, drop down to an E8400. Very much like the Q6700 vs Q6600 your not gaining much besides a lighter wallet.
I think you have you ram speeds and FSB a little mixed up. The 1066 of the chip refers to intel's "quad pumped" numbers which ends up being 266Mhz FSB speed. The "1066" of the RAM refers to the "double data rate" of 533Mhz FSB speed, which the quad will not hit. Your chip will likely hit a wall around 475Mhz actual FSB, or 950Mhz in DDR2 terms, or 1900Mhz in Intel's quad pumped world. A little more confusing that necessary isn't it.