All i can tell you is what I have. I paid $250 for it used.
http://www.treadmillsusa.com/index.htm?itemktp2000.html
Keys PRO-2000 Folding Treadmill S.E.S.
It's not EXACTLY like this one, but it's the closest I found. They don't sell the exact model I have anymore (Pro 850). Anyway, I really like it. Of course, it's not the quietest or the most expensive. It was $900 or so new, but the girl that was selling it wanted to get rid of it. I have been running on it for 6 months now and haven't had any trouble with it. The incline wasn't working, but I opened it up and blew out all the dust and it started working. (keep in mind, this treadmill is about 6-8 years old.) It's 3.5HP, has 9 workout programs, folds up, weight capasity is 250lbs ets.
Anyway, it's a Keys. Good brand as far as I'm concerned, but this is the only one I have had. I was watching the paper for one for a while and never saw any. Then I put in an ad saying I was LOOKING for one and we got a bunch of calls.