There's a near new one on the trading post for sale. But, before you do that consider a few things.
First off, you have a misconception about modifcations. Done properly, your saw will actually gain lifespan not lose it. Consider that the manufacturer has too satisfy many oversights that choke the saw down quite a bit. That said, I'd not spend the $250 or so too "woods port" a Husky 55. It's just not cost effective. A muffler mod a retune and you'd see some gains and the saw would run cooler. (cooler is better).
Now lets look at the 361 issue. You are looking for more power but like the size and ergonomics of your 55. The 361 will have more power but not a huge amount more, maybe 1hp and it's pricey. I have a feeling that you are looking for a single "do it all" saw that your comfortable with? If that's the case, you want a 70cc class saw. You'd have appreciably more power with only a small weight penalty. If I could only have one saw, this is where I'd look.
If you are only doing home firewood and are cutting hardwoods in your area of upstate NY, the 361 is an excellent choice all round saw but again quite pricey. You really ought to look at the Dolmar/Makita 6400/6401 for a well built upgradable all around solid firewood saw. At the moment you can get the Makita version new in the box for as little as $375. There is no better deal out there.