If you are looking to only quilt on it - not piece or do anything else, you can look in to a Bailey Home Quilter. They are suitable for sitting down or on a frame so if you ever decide to get a frame you will be set ;) and they are inexpensive, work horses that are not finicky about thread. There is a yahoo group for them and people that have them adore them. :)
http://www.baileyssewingcenter.com/test.html
You can get a classroom model from them that is discounted.
They come in 13", 15" and 17"