If you haven't looked at everything on the market, that's in your price range, you owe it to yourself to try everything out there. A longarm is a much more personal decision than your regular machine. What I like in a machine might not be what you are looking for. Most dealers will bring the machine to your location and set it up for you and give you a lengthy training session.
There are several machines available depending upon you price range. The HQ16 is nice for a mid arm and depending on the table and features you choose can run up to $16,000 if you go with the robotic system. At that price it opens up a full spectrum of true professional longarms like the Elite A-1, any of the APQS models, some of the Gammills, the Innova, the Noltings, the Tin Lizzie and others.
Test drive everyone that you can get your hands on and not just for ten or twenty minutes play with them for an hour. See how your back feels, does it move well or is it difficult to steer around. Does it, in standard form, fit into your space. For example, Innova recommends a space of 16 x 6 minimum for it's 14' frame. That's a big chunk of real estate. Rule of thumb is 2 more feet in width and at least 2 more feet in depth. Are you capable of doing your own maintenance ? With a longarm unless you live in the same city as the dealer, you will probably have to do your own maintenance and some smaller repairs, like timing the machine and replacing belts. There are so many things to consider to a longarm purchase, dealer and manufacturer support usually are at the top of a very long list.
Spend a few days looking at the topics on this board
http://mqresource.com/forum/index.php?act=idx, you'll find a wealth of knowledge with an even larger wealth of experience. It will really open up your eyes and your mind to what longarm quilting is all about. There are several award winning national quilters that belong to the board and it's a grreat place to start your research.