I promise I'll only post once, but you really can quilt on a treadle sewing machine.  They will sewing through most anything and once you understand them, you can usually find a perfectly usable one for much, much less than the most inefficient electric machine.  If you really get into it, you can even get a treadle machine that zig-zags.

Here is a quilter (and collector's) page of quilts.  What I want to show you in this photo is the amount of room this machine has under the arm for the quilt

http://4.bp.blogspot.com/_AmILpRyS6fU/SNqS_g_JEfI/AAAAAAAACQQ/lfxjUJkXPTU/s1600-h/Singer+Centennial+15-88+treadle.jpg

That is an especially beautiful example of a Singer Model 15-88, but one that is not so pretty may sew just as well.  That particular model is nice because it has the reverse stitch. 

Here is her main page:

http://treadlequilts.blogspot.com/

As people were posting about not having room for the bulk of a quilt, I was sitting here looking at an old Singer that I am planning to work on when I get 'round to it.  There is so much more room on the bed than on my electric machine.  This old machine had been removed from its treadle cabinet and converted to electric at some point.  I'm going to undo that and see how it sews.  If it works well, it will just go into the cabinet that's sitting here.  It was my husband's grandmother's but someone really beat the machine to death.