What is the price of the Makita DCS510 with a 20" bar?
Bailey's sells them for $365.
Big33:
If I'm remembering correctly, the Makita saws are basically the same as the Dolmars with similar model numbers, just a different color. I know the Domlar PS-510 is a decent mid-range saw - not up to their PS-5100/5105 pro saw, but then the price isn't up in that range either. One knock I've heard against the DCS510 is that it's a bit heavier than a number of other 50cc saw options, but if that doesn't bother you, they are good saws for the money.
A good 50 cc will be a bit slow at the larger end of the size range you mentioned (especially if you are cutting hardwoods), but it will work -- just keep the chain sharp. I did exactly what you are doing with a 50cc Jonsered 2152 (twin sister saw to a Husky 353) for several years. Same HP as the DCS510, but weighs about 1# less. It was rare that I was cutting 20". Most of my cutting could be handled with a 16" bar, so that's what I kept on my saw.
I will second thecfarm's suggestion that picking a good dealer in your area is just as important as picking a good saw. If you can work on them yourself, maybe that's not as much of an issue for you.
John