I say test drive every machine you can get your mitts on! A large show is the best and they usually have deals. BUT, that being said, when I decided what I wanted I looked on some on the 'gently' used sites and found one local to me in my price range. Don't take someone elses word and just buy. You need those opinions, but you need to see what fits YOU too.
here are two links to get you started!
http://www.houseofhanson.com/formerlyowned.html
http://www.apqs.com/quiltboard/forumdisplay.php?fid=31