Remember that if you use a frame, some of the throat space will be lost to the take up bar. So your 6 inches will become 3-4 inches.

The throat of the Juki is 9 inch, so with the lost of the take up bar, it still leave 6 inch (or I am missing something?)
There is no longarmer in my area (quilting is really not a popular hobby, so there is no market for this kind of business) and shipping charge in Canada are very expensive.
There is no dealer here, no quilt show where to look and try different setup... it would help to make up my mind. You quilters in the US are so lucky!

I have a Bernina 820 sitting on a Bernina frame. The 820 is just a little bigger than the Bernina you have. I am happy. I have plenty of room to do my free motion quilting even at the end of a king sized quilt. My husband put together the frame with no problem, but the quilt loading instructions were poor, so if you buy a Bernina frame PM me and I will give you some tips. Good luck on your decision.

Save your money and get the largest throat space that you can afford. I have an HQ Avante and love that machine. Throat space is so very important ...I can load a large quilt in 10 minutes with the Leadergrip system. It saves so much time so you can get right to quilting the quilt. Good luck!!