I also have an HQ16, bought it second hand, and love it. So far the only problems I've had with it are 'cockpit errors'.
I use a pcquilter with it on a pinnacle frame. I don't really like the frame, but it was a package deal. Someday I'll upgrade the frame, but for the kind of quilting I do, the HQ16 is plenty big.
Good luck on your search!