The trouble with putting a different machine on the HQ frame is that the way the carriage is designed it'll only take a machine with the rollers/stitch regulator that fit it. I believe that only the HQ and Baby Lock machines are made this way. You're right though the HQ frame is a really great one! I don't know if you have an HQ or BL dealer in your area, but personally I'd go with one of those. There are 2 frames that fit the Avante, the Pearl (I have this frame, it doesn't have the extra bar, but other than that it's the same and I really love it!), and the Studio (I think that's the name of it). I've used both. The one w/o the bar is slightly less expensive, and if the bar really matters to you than I'd say get it. They're both great frames though. They move so smoothly.
Anyway, to answer your question, no, I don't think you could put anything but an HQ or BL machine on their frames. But this would be a big purchase. You want to be happy with it for a long time. Buy what you know you'll be happy with long term. You don't want to end up wishing you'd gotten something else.
Good luck!
