Ideally, I'd buy 3 machines to supplement my Bernina 1230 (which I wouldn't give up for anything!).
#1 would be a Pfaff for the easiest accurate piecing because of its IDT.
#2 would be a stand-alone embroidery machine if I decided I wanted to do embroidery. This is because I would want my embroidery machine working away independently while I am piecing or quilting on another machine. When you have a machine that does both, you can't be sewing while you are embroidering.
#3 would be a mid-arm or long-arm machine for quilting on a frame. The HQ16 sounds like it might be my choice for a mid-arm; not sure yet about a long-arm. For quilting in a frame you really want the deepest harp you can get to allow for as much depth in your quilting as possible. A large quilt takes at least 6" of harp space when it is rolled, so you have to subtract that from the machine's harp to figure out how much space you have left to quilt with. Regular sewing machines like my Bernina just don't have a deep enough harp for serious frame quilting, IMHO.
I love my Bernina 1230 because it is completely reliable and purrs. The only things I could wish for on it are a bobbin-getting-low light (hate piecing for ages only to discover I ran out of bobbin thread yards ago!) and the IDT feature of the Pfaff. Piecing is more easily accurate with a walking foot, and with the Pfaff you don't have a big bulky foot in the way. I suspect my 1230 makes a slightly nicer quilting stitch, though.
It's too bad one machine doesn't do everything the best!