One thing I guess I should add- I'm running with a full chisel, even on the longer bars, so that might make a difference.
I always thought the 660 was a little of a dog as it came from the factory. A better muffler and retune helps a lot. EPA compliance stuff really hindered the 660, 260, 460, etc. from the factory.
I've never run Huskys, so I can't compare. I know I was really happy with my 660 with a 28, full chisel chain and a 7 pin sprocket. I've got a 36" .404 full chisel on it now, and it pulls it fine, but it isn't going to be winning a race with the bar buried. It was a little faster with the 36" 3/8" bar. Big old dead, dry white oaks will make it earn its keep