I'm no expert but my buddy has been running a rancher for his woodpile for several years and it has been great. He is really hard on his equipment too, I won't let this guy use any of my stuff, but his saw has never failed him.
Not a pro, but I've had the Husky for a good long time. I am running a 20" bar on mine and that may be a bit optimistic. I like it a lot, but I like the Efco (Cub Cadet) better. My boy likes the Husky best, but has not run the Cub yet. If yours cuts as much wood as mine has, you will be very pleased.
The 50 Rancher should provide good service as a light firewood saw.
I would stick to 16" bars (or preferably shorter) on that saw, and use narrow kerf bars with Oregon 95VP chain to make the most out of its relatively limited power.
I would agree with saw troll, I just put a 16" narrow kerf bar with a arbor pro chain on my 2152 and it cuts like crazy. I still have the larger 18" bar and chain put away for bigger jobs. I got a really good deal from Bailey's on the bar and 2 chains I bought. Keep in mind the arbor pro chains are not low kickback chains, the chains work great on the higher reving mid size saws. The only trade of is there is no anti kick, you just have to pay antention to your tip.