Janome makes a real quality product, but you're looking at the wrong line. For quilting, check out their quilting machines. I've been using a 6600P for years and have quilted several large quilts on it. True, it can be a squishing exercise moving and turning the entire thing under the throat, but this machine is larger than usual and about as large as you will get without moving into a long-arm. Spend the money now and buy as much machine as you can afford as you will grow into it as your skills develop. Here's my suggestion (without going top professional):
http://www.janome.ca/machines/Horizon/intro1.php