Other than the larger throat, quilting doesn't need fancy stitches. Straight stitch for piecing. Free motion capability (drop feed dogs) for quilting. You already know you want a few fancy stitches - that's still not a high end machine, and I don't think one is necessary. My old Kenmore, which I bought for about $300 does a blanket stitch.
The throat size - after quilting for 7 years I would definitely pay for a decent throat. I have about 7-8" on my machine, and it is a pain in the neck to do anything much bigger than a baby quilt. I have done it however - all the way up to king size. If you can get a larger throat without breaking your budget, I say go for it. But don't let them push you into fancy embroidery stitches and what-not. And it's possible to do a lot with a smaller throat, with a little bit of creativity and perseverance, if you can't afford the big throat now. After 7 years, I'm splurging on a long-arm machine (which arrives tomorrow)