If you are able to "test drive" different types of machines before you choose one, it will be worth your piece of mind....
I started off with a regular machine, a small frame, and 2 conference tables pushed together. It wasn't long before I realized that I wanted more throat space. I checked into lots of different brands on line, and the companies gave me the names of people who were happy to let me come over and try their machines.It took a little bit of footwork, but I am so happy that I did it that way!
If you have any shows nearby, try shopping there, and do lots of test drives. Always ask about the throat space, and visualize how much room you will have when there is a rolled quilt on the machine. I have a neighbor who gets frustrated every time she has to remove a quilt, turn it around, and then try to finish the other half. The throat space is just as important as the length of the machine -- and sometimes MORE!