I am in the same boat as the OP. I would love a larger throat machine, but the budget just does not allow for anything close to the cost of a HQ anything !
I currently have a Brother PQ1500 that I LOVE. I have quilted a Queen size on it at my table, but it was a test of will. I have had it on a Grace frame in the past. I HATED this. Small throat space on a frame = very limited design space.
The other problem I ran into was endurance. Standing up at the frame is not the same as standing up at a cutting table ! Your not just standing ! You are walking the length of your quilt , AND moving the machine at the same time. This takes practice ! It also takes alot of energy and unless your in fantastic physical shape ( which I am not ) your body is going to hate you.
While having a frame means you no longer have to baste your quilt, it DOES mean you need to load everything onto your frame. I think quilt shows should have demos set up so that you can see what is involved in THAT part of frame quilting, but I have a feeling it might lower their sales ! It is not easy ! Yes, there are zippers and other leader options that make it easier, but it still takes alot of work to load a large quilt by yourself and keep everything very straight.
A frame is going to take up space. ALOT of space ! Personally, if I had to keep my frame in the basement, and the rest of my sewing things were in another room, my frame would not see me much !
I have looked at the Block Rockit, but it is not available on a table, only the frame. I have also looked at the Bailey, and while they have a longer throat space, it does not have a high throat space, and when you are bunching a quilt at a table, that means less space for it to squish into. The Sunshine 16 has perked my interest though.