For a new machine, it really depends on (A) your budget, and (B) what you want.
If you want a lightweight machine to take to classes, then a Janome Jem can be a good purchase (lightweight, good for piecing, not good for quilting). If you want something for machine quilting that has a lot of bells and whistles, I think it's hard to beat the Janome 6600 (which I think are in the $1,000-1,500 range) because of its extra-big harp.