I would get a sit down longarm, especially if you are space limited. You will be able to quilt just as you have in the past but have the luxury of a larger throat... and get yourself an embroidery machine as a bonus
If you are able, go to a big quilt show and check out the machines. There are lots of sit downs to choose from... and soon Juki will also be releasing a sit down with a stitch regulator option as well. Having said that... I bought a Tin Lizzie sit down. It does not have a stitch regulator but I did not need it. I was already used to free motion quilting on my home machine. If you already do free motion quilting, you will not need the regulator. Spend that money on something else (like that embroidery machine or supplies or anything else you might want)
I liked the HQ sit down a lot and was going to buy that but chose the Lizzie instead for several reasons - the biggest being that I did not like the way the machine was orientated. when you need to turn the handwheel, you have to get up and go around to the back of the table... and then there was the table. You have to pay extra for the table overlay to fix their table height problem (the machine sits up a little higher than the table top so if you plan to do any ruler work you can't unless you buy the overlay) and then there's the table itself. The Lizzie table comes standard with a large extension on the back of the table, almost doubling your table. I will admit that I also added another table to the left of the machine to support the weight of large quilts. I have already quilted a king size with no space issues. I do love my Lizzie. The Lizzie was also cheaper. With my left over fundage, I bought a Juki 2000 which I absolutely love for piecing and small quilt projects. It stitches incredibly fast. I swear I have doubled my productivity thanks to that machine... and when I've needed to make thick projects it handles it like a pro. It doesn't fuss over super thick bulk like my Janome used to.
Do you have any big machine dealers near to you? Having local dealer support is nice. I opted to buy out of state but it's okay for me. I was able to save a lot of money that way.
I would avoid the Bernina 830... I also have a very close friend with one and it is a headache.