I wouldn't look at any of the cheaper machines, as they mostly only have a 4 or 5" embroidery field, and once you're used to quilting with it you will invariably become more adventurous and want to do 'bigger and better' things. So I think you should look at the bigger machines. You will want to quilt square blocks as well so will want a larger embroidery area, at least 6 x 6'.
I have Brother machines, and a Pfaff, which were top of the range at one time. Have always found the Brothers so user-friendly - the Pfaff just sits waiting, as I am self-taught and this one takes so much time to work out, and then later I forget what I did. However, all machines except one Brother were bought pre-loved for a third of the new price, and have not had problems with any. You could try your closest machine shops, they will often have or know of someone selling a machine to upgrade.