+1 on the extra capacity. 5x6 bales can be heavy, especially if lifting them high to stack.  Just because a skid steer is advertised at x lb lift, that doesn't mean you can do it at any height, on any surface.  5x6 bale CG is further out than the standard rating point also as I recall.  Go larger than you think.  

A big thing with used skid steers, as with used fork lifts: find out where and how they have been used in the past.

Should be able to get into a JD 326D or 328D for that money.  Not sure on how many hours are too many, we usually trade before 2000.  I have spent a lot of time in Bobcats, NH, and Deere's.  I think they are all good machines, but I always felt like the JD was better balanced than the other two, even though the NH has the same lift.  I got some cement bunks from a friend who had a Bobcat, and he couldn't lift the bunks with one skid loader without tipping, we could easily lift them with our 326 and both skid loaders were rated the same.

If you are new to skid loaders, start with the joystick (iso) controls, once you get used to them, they are less tiring after a long day.  Garvo mentioned you being a big guy, stay away from the 300 series Deere with the door that opens up.  They are good skid loaders, but the door is a pain for bigger guys.  The biggest regret Dad, my brother, and I have right now is we did not get TRACKS.  Tires are good on solid ground and cement, and ride nicer, but the amount of work you can get done, and places you can go with a track machine is amazing.  Someone mentioned above that you need a heated shop for tracks, I think that can be debated.  Park it on plywood and scrape any mud out the the undercarriage if it is going to freeze if you don't have a shop.

I bought a used JD250 for $10k, put a couple k into it at my JD dealer, added some weights in the back and have a very useful tool. It will lift 5x6 bales but not as stable as a larger skid steer would be.  One thing about JD is you generally have parts and service nearby.

ISO sucks till you get used to it, then everything else does.

I was going to tell of my dislike of Case in my first post, but it is Sunday and didn't want to hurt the neighbors feelings, but I see someone convinced him to drink the tainted water.

Johnny, is your new one ISO?

Give it time, when we first got ours, Dad wanted to trade back to regular hand-foot controls.  I was sort of on board with the idea of going back to the old way also, but as time went on we all adjusted to iso.

Your right in the fact it can be a pain, heated shop is best.  Brother worked for a tiling business the guys would always go through the trouble to get the tracked skid loader going in the cold just to not have to use the wheeled skid.  I have helped a friend break his loose one day and it wasn't too bad, I just think back to how much more he can do with the tracked skid compared to ours.