Darby
I completely understand your "but WHAT should I shop for question"
If you want one machine to do it all (piece, quilt, and possibly even garment sew) then you need to look for ONE machine that will do ALL of that.
Some features I NEED for quilting: Wide harp area (9" minimum, preferably more), needle up/down, extra high presser foot lever (easier to position the quilt under the needle), the ability to drop the feed dogs, and unless you have a sewing table that you can drop the machine into for a full flat bed - make sure your machine comes with a nice wide table to slide on to the side for stabilizing the quilt . It's also important to try both the walking foot and the free motion foot on the machine you are thinking about buying to make sure you like the way they work. Make sure YOU change both of the feet so you know if they're tricky or easy. Look at all the available walking and free motion feet to make sure they have the kind that you want (ie walking foot with a 1/4" guide is helpful, and do you like a closed or open toe FMQ foot, and do you prefer metal or plastic?).
Some features I NEED for piecing: an integrated walking foot (OK I don't "need" it but your $2K budget should not be a problem getting it! I LOVE mine with 1/4" guide for piecing long strips), micro-step needle position (I want to be able to change the needle position by the width of a thread for accurate 1/4" seams - not just left, right and center), thread cutter (again - don't need it but your budget is not a problem finding it), multiple stitches and the ability to adjust the length and width (if applicable), and an easy to remove bobbin plate and easy to clean bobbin area (I'm a constant cleaner!).
Good lighting is a bonus, but you can get around that with well positioned Ott light (o similar). The lock stitch is nice, but to be honest I rarely use it. I might start
Do you plan on taking it to class often? Weight might be a consideration, or if not the weight, see if the dealer will throw in a wheelie bag with the machine, or consider the price of buying one (if you don't have one).
Test drive the machine for all the functions you want to do, make sure that YOU are the one performing all the functions like changing presser feet, winding bobbins, etc. Make sure your comfortable with the foot pedal, or find out if a different one can be used. Also, don't be afraid to look at high end used machines offered by dealers. They usually service them before they sell them, and offer a limited warranty, support, and classes.
If it was me on a 2K budget I'd look at the Janome 6600, or if you can find it at the right price a Janome Horizon 7700. I have the 6600 and would love the few extra inches of harp space the 7700 offers. I *think* my dealer offers the 7700 at $2199 with the wheelie case, 12 spools of thread, and the folding table that the machine drops into. If I didn't already have the 6600 I'd snatch that deal up!!
Good luck!!