I could quilt on my dsm, but it was hard on my back and shoulders. After trying out frame quilting at quilt shows, I knew that was a lot more fun for me! Took me about a year to research setups online to find something I could afford. Knew I wanted a Hinterberg stretch frame and Voyager 17 so, when someone in my quilt guild left a flyer at a meeting wanting to sell this setup, I bought it. It was about half the price of a new sitdown machine.
I find frame quilting to be ***much*** easier on my back and shoulders, plus I can finish a quilt much faster this way.
If I didn't have the space for a frame, I would definitely consider a sitdown setup with a large harp. Alternatively, if you really don't want to spend the money, it's a good idea to find ways to cut down the bulk that needs to go under the sewing machine arm. I did a few quilts this way by splitting the batting into thirds, quilting the middle first, then re-attaching one side at a time and quilting that. Debra Wagner has *excellent* instructions in how to do this in one of her books, but Marti Michel also describes this (plus other ways to cut down bulk) in her book:
http://www.amazon.com/Marti-Michell-...dp/B0002J5GX0/
For me, ergonomically it makes a lot more sense to quilt standing up -- whether on the frame or my dsm. I did find it much easier on my back and shoulders when I listed my sewing machine onto my cutting table and placed a styrofoam "table" around it. Biggest issue with that was making sure the machine's foot pedal reached the floor.