I took a machine quilting class for beginners at my LQS and the teacher had quilted plenty of queen and king size quilts on her regular home sewing machine. It's all in how you set it up and lots of practice. If you can't take a class use your 40% off coupon at JoAnn's and get Harriet Hargraves book Heirloom Machine Quilting. The teacher I had was great. The first thing she told us was never listen to anyone who tells you there is only one way of doing things. There are lots of ways to do everything. You just have to find the one that works for you.
Also I bought a Fun and Done pattern and the templates and this is an easy way to make a quilt of any size with any sewing machine. Google Fun and Done quilts.