How often are you going to use it, how mechanically inclined are you, and how much money do you want to spend?
To go up to a 36" bar, you need a saw that's at least 70cc. Saws in the low 70s may need a high output oil pump for the bar. If you run it a lot, get a Stihl or Husqvarna. If you don't run it a lot, or you are pretty mechanically inclined and don't want to spend a ton of money, I'd get a clone. I've been running a G660 with a 28" bar and occasionally a 42" bar for a few years now and love it. Its not my main saw, but when I want something longer than 18", that's what I grab. There were some parts that I had to replace right off the bat (clutch, high output oil pump for the 42" bar, mounting screws for the handle and spikes), and there were a few more that I replaced because I wanted to (dp muffler, starter pawl), but it has been well worth the $321 I spent getting it to my door. If you're not mechanically inclined, reach out to bluesaws.com. They will sell you one that they've gone through and checked out OR they will build you one that's ported for about half the price of the OEM saw, and I'd put their built saw up against an OEM saw any day of the week in both power and durability.