A Case 580Ck for 11K seems steep unless it is very cherry. But without location and photos of machine it is hard to tell.
A true backhoe like the 580 is a requirement in rock and hard soil. What do you plan on doing with it? 4wd is nice, but depending on your use it might not be a requirement.
I'd have a different opinion on most of those things, but that could be no more than using the same tractor in different climates and soils.
We have granite based "soil" here in the western Rocky Mountains. It's not like the sandy clay-based loam east of the Mississippi. Ours has no clay at all and the "mud" doesn't stick to tires or shoes. Ours is more like sand and gravel. But we do have snow and cold.
Sooo..... here a 2wd will do most of what a 4wd will do except in deep snow. You can't get stuck with any loader/backhoe anyway, and neither will work on ice.
As for pricing, 11k seems a little low to me. I would be reluctant to buy any backhoe/loader for under 15K unless I knew it and trusted the person selling was deliberately giving me a special deal. After all, new set of tires all round will set you back $2K. A full routine service can easily go $500 in lube & filters alone. A good set of batteries (they typically take two) isn't cheap either. The upside is that both tires and full service are good for a decade....
We are keeping the JD310. It's not worth selling, and it is nice to have something with all that spare power. It can literally lift a car out of a ditch.
But strong as it is, the Kubota M59 gets ten times the use. Particularly in our granite soil with so many boulders. The Kubota has plenty of spare power, much more accurate controls, has a thumb strong enough to crush rocks, and will lift a couple of tons.
There are few jobs that the 310 can do that the M59 cannot. Mostly the 310 is better at moving large bucket loads long distances. And it has a cab.....
Something to keep in mind is how the visibility is from the operator's seat to the front bucket. These yellow commercial loader/backhoes don't have a 3pt hitch, so you end up using the loader & BH buckets creatively to do a lot of jobs. You can see the BH bucket pretty well, but you also need to be able to see the loader bucket.
After power steering, an SSQA front hitch is the best thing that ever happened to any front end loader.
rScotty