I just bought a Tin Lizzie sit down model - it can be converted to a frame if I ever decide to go that route as well. I've done the frame once and didn't really love it, so I doubt I would convert to a frame.
In fact.... I'm waiting for the UPS truck to arrive now.
I got it at a quilt expo. It was $4k and I got a lot of free goodies to go with it
I'm not sure where you live, but if you are in the southeast, I can recommend a dealer if you go Lizzie.
I would strongly suggest that you hold off on buying a machine until you go to a quilt show that has A LOT of machines both stand up and sit down for you to try out. I don't think you'll be able to get a new framed machine for $5k at a quilt show - you'd be able to get a Bailey, Voyager or a Sunshine for that but if you are looking for new then you are in the sit down category. I'd suggest the Lizzie, HQ Sweet 16 or Babylock Tiara - the HQ & BL are identical machines & tables. They both have an optional stitch regulator as well. The Lizzie does not at this time but I didn't think I needed it after playing with it for awhile.
No matter what you get, I'm sure you'll like it! Also - keep an eye on Craigslist in your town and surrounding driveable areas. If you wait long enough, one will come around at a price that you like