You need to determine how big the quilts are going to be to decide how big the 'throat' space is you will need. For larger bed size quilts I would suggest at least a 10" throat. I've quilted a queen on a Bernina 153 QE and my shoulders and back were killing me by the time I was finished over a several day period. I don't know what size dsm has that size throat.......take some research for you to do.
Machine brands: I own a Babylock, Bernina, and Necchi plus a Gammill Class+.
Purchase the best quality you can for what you can afford to pay!