I suspect that the Little foot frame would be an extremely tight fit in 1 6'x6' space UNLESS you never have to get behind it for any reason.
Had a HQ16 for years, no stitch regulator, on a frame and with the pc quilter. The HQ16 was a work horse, never had a problem with it, never had it professionally maintained - DH is the handy type, and very carefully cleaned and oiled it as necessary. The computer the pc quilter was on was failing so I replaced the system with a Qnique 21. It works well, but I do miss the HQ16.
The only thing negative I can say about the HQ16 is that the user manual was way too thin. It covered the basics, but that is it. That is probably so that you will take it to be maintained professionally, but those machines are heavy to cart around. Perhaps they want to make house calls.
However, if you are the handy type, you can find videos on you tube these days that explain most maintenance issues and how to handle them.
Please note that un-clamping the quilt and turning it around will work with some motifs/pantos, but for others it will mean turning the motif/panto around, too. There is always some new challenge awaiting, right?