Just went through this a couple months back.

If looking for new, anything in your price range will be crap. We bought this Smooth Fitness unit, delivered for a little under $1000. It's not quite gym quality, but very close. It's an excellent unit for the money - well built, quiet, and it has the heart monitor built into the handles. Wife and I both use it frequently, as do our dogs.

For $750-1000, you can likely find a nice used commercial quality unit - but the proposition is risky. There are plenty of used gym/commercial units in this price range from higher end manufacturers listed at places like craigslist, but you can quickly ring up a hefty repair bill if you don't know what to look for.