What kind of wood are you cutting that you're gonna need a 660 to pull a 24"? You can pull a 24" with ease with either 440 or 460. Even in hardwood. Alot of guys do prefer to use as small as bar as possible, and maybe it's just my West Coast mentality, but let the bar justify the saw. They'll say that you can cut faster with a 660 wearing a 24" than with a 440 wearing a 24", and with the bar buried, the 660's hp should pull it faster than the 440. But what's the point of lugging around a powerhead that weighs almost 17 lbs, just to pull a bar and chain that a 14 lb saw can practically just as well? I'm also not saying put on the biggest bar the saw will hold just because you can, but I'd have no problem putting a 32" or 36" bar on that saw, and even bigger if you really need it. This same thread came up on another forum recently, and there's guys running 40" and 42" on 660's. Are you buying the 660 just to have a 660, or are you buying it because you need to run a 24" bar? If that's the case, put the 24" on your 460 and have at it. And the "best" size bar depends on what you're using it for. If you're felling trees 25"-30" you don't need a 36", though the saw would carry it. Go with a 28". If you're milling, get a 32" or 36." If you're cutting anything less than that, the 660 is overkill, and will tire you out.