Can the 440 be modded to rip a log like the 660? As for the 650 vs the 660, would the difference in a few cc's be worth the price? How much do the 650's usually run?
I've run a 660, and the 650 feels pretty much the same to me. I bet you wouldn't notice the difference until you were in really big wood and bars over 36". TBH I can't speak from experience on that, as I've never run a bar bigger than 32", but the 36" is in the plan. I have owned a 460, and do own a 650 and 440, however.
The 440 can never come close to the 650/660, especially as the wood gets bigger. The torque just isn't there. But, the 440 is way easier to lug around and much handier.
The 650's can be had for around $730 in Washington, about $250 less than the 660. The 650 with the factory dual port just rips!
Good luck!