I can't comment on any of the Kubotas or Fords. Personally, unless you're mechanically inclined, I'd stay away from the Chinese tractors (of course, I think China is our greatest enemy too). And, I wouldn't even consider grey market.
However, as far as the Deere's you mentioned, the 750 is probably a bit small for 12 acres. The 790, a sweet tractor, is borderline. So, the 870 would be the best choice with the 790 a close second. That's of the Deere models you mentioned...you might look at the 970's and 1070's too.
Now, if your 12 acres isn't all cleared (say 5 acres wooded, the rest improved), then the 790 would be a great fit. The 4300 machines would also be an excellent choice...in fact, probably the best choice for 12 acres. The 790 and 4300 series Deeres are both midsized chassis, so they're pretty close in size. Both should work well in the wooded areas. FYI, I paid about $12500 for my 790. I did look at a 4300 Deere (with sync-shift and a loader) for $14200. That was a pretty nice machine. My 790 also has a loader...very robust, but doesn't have the capacities of the newer designs.
Just because I said I couldn't comment on Kubota or Ford doesn't mean they're bad...far from it! Just not enough first or second hand experience to comment.
As long as the tractor doesn't smoke excessively after warm up (expect some smoke when under a hard load) and it pulls well, I wouldn't have any concerns with up to 1500 hours.
Just makes sure the PTO operates with an implement hooked to it. If it's a dual stage clutch, make sure that works OK, or negotiate down to cover the repair cost (about $1500 so i've been informed by my dealer). As far as the rest of it....well, it depends on how pretty you want the machine to be. It is a tractor, so expect a used machine to have some dents and rust. It sure would be nice to have any maintenance records, but I wouldn't expect that.
Good luck!