I don't have a recommendation for a good treadmill, but I can tell you one to stay away from: Keys! I spent $1200 on a Keys 4700. Within the first year, it had to be serviced at least four times, and finally was replaced. The second treadmill had the exact same problems: belt slipping, bearings went out in the front roller, computer issues, etc. My DH managed to fix the problem with the roller (he thinks there's a design flaw), but it still has computer problems. Nothing like jogging along at a nice clip when the treadmill just STOPS. . .
I don't know what the price range is, but Cybex is gym quality-- I think that's what my husband uses at the clinic where he works.
Good luck!
L