I have a Jonsered (Husky) CS2240, an Echo CS-590, an Echo CS-501P, and a Husqvarna 562XP Mark I. The last two are bona fide pro saws. I'm not including pole saws and cordless.
There is a lot to be said for the CS-590. Although it's a consumer saw, it has a lot of pro guts. It's not a plastic clamshell you throw away after two years. On the down side, it has a nutty hole in the main jet that will prevent you from tuning it properly, so you have to accept an inferior tune or push the jet out and replace it.
I wouldn't let choked-up carbs slow you down. I doubt saw manufacturers expect serious people to run their saws as they come from the factory, with ridiculous EPA exhausts. The 501P has a muffler part you can literally lift out and throw away after removing some screws. They didn't make it that way by accident. As for other saws, you can do them a lot of good by drilling holes in various areas of the mufflers. Information is all over the web.
I modified my 590 quite a bit, and it is very good now, but it only has a 20" bar. It might not be enough for OP.
Whether you would be concerned about violating your warranty with mods would depend on your dealer and your confidence in your ability to do your own work. Those warranties aren't great anyway. I mod at will, because I know how awful the local repair places are.
The Husqvarna is a pain to start due to overheating issues caused by a poor design, hence the "Mark I" and "Mark II." The Mark II is supposed to be better. The saw I have is somewhat faster than the Echo even with the Echo's mods.
If I were cutting big trees, I would strongly consider an Echo 7310. They are old-fashioned compared to fancy saws with electronics, but the simplicity means you can understand them and fix them without wacky software.
Vibration is something to consider. The older you get, the more you need to think about permanent damage. They say Husky is best, but I wouldn't know.
