I highly recommend a Kurt Kinetic. I am using a 2nd hand one now and it is great. It is extremely quiet, smooth and mimics riding on the road better than any other I have tried so far. A few buying tips - REI has a 20% off coupon right now if you are a member. If you are not keep you eyes on Craigslist - they show up on there for a fraction of the new price. There was one on my local CL last night for $100 in fact.