I have a Brother 1500s and a Janome 1600, basically the same machine with 9" harps. I had the Janome on a frame and used the Brother as my "daily driver" for piecing. I purchased both machines used for $400 each. If you want used (or "pre-loved") machines, don't stop at checking with your local dealers. Put the word out amongst all your friends (including the non-quilting ones), your local quilt shops, and your guild that you're in the market for a good, used machine.
I strongly, strongly recommend you get the largest throat that your frame and budget will allow. I ended up being very disappointed with the 9" harp, because once you get the quilt partially quilted and rolled up in that harp, you end up with only maybe 3" or 4" of quilting space.