There are two different ways to quilt -- one is on a frame where you move the machine; the other is sitting down at a machine where you move the quilt. Most people prefer one method over the other.
If you attend the quilt show in Paducah every year, I would suggest that you try out every frame quilting machine they have at the show. There is a lot of variation among the different frame setups. My personal "dream" machine is an Innova with lightning stitch.
Machines themselves can be categorized as shortarm, midarm, and longarm depending on the area under the arm (harp). You probably tried out a shortarm on a frame; these are very limiting. Most frame setups use a midarm machine (my Voyager 17 is a midarm) or longarm machine (which start at about 18" of space under the arm and go all the way up to 26" or more).
There are several sit-down machines that have large harps: the Sweet 16 and George come to mind.
What is your price range? Chances are, if you are looking not to spend a lot of money, your choices will be limited to just a few brands.