I agree with the pp5020 for a cheap option. $200 brand new. It's kind of heavy but not too heavy. I take it in the tree to chunk down trunks. There are a lot of negative reviews about them. I don't know if I just got lucky or I haven't used it enough, or I just keep it clean and correct fuel mix... but mine has been good for about a year now.
Also Stihl ms 211 or 251, $300-360 i think.. I have a ms 210 and it cuts very well for how small it is.
A lot heavier but good option is a Craftsman 3.7 or Poulan 3800. Old saw but its 61cc and with a muffler mod it really rips. You could probably find a used one for a good deal. I got mine rebuilt, new lines, new plug, new cord, etc for $215, put a new power match bar and its really worth it. Rips.
If you have to go with commercial grade saw I couldn't help you because I can't make that decision myself.