Hi and welcome!
I have had Singers, Brothers, and most recently a Janome 7700 and a Juki HZL-400.
My 1st "I am serious about machine quilting" machine was a Brother PC-420. It's in your price range. For the price it has a lot of great features. I will post a link to Amazon, which has great info/reviews. I also purchased mine from there. Now I know it's a big decision on whether or not to buy a machine on-line. Everyone is different, and for me I have bought several machines on-line...I have also had great customer support when needed..but I know that's not always the case. One thing I really like about this Brother is it has auto thread cut and a knee-lifter, which I had never had. But once I got it, I don't know how I quilted without it
.
http://www.amazon.com/Brother-PC420P...brother+pc+420
I then bought a Brother PQ-1500. It's a straight stitch only machine. It has a pin-feed system which is wonderful for piecing. It also has a 9" harp/throat, which is great for quilting. I can't get the link to post right, but you can type in Brother 1500 and Amazon has info/reviews on it, too. This one usually costs around $650-$700, so it's a tad over your budget. (I sound like a realtor on House Hunters TV show..
). As I got more into quilting I bought the Janome Horizon 7700, then the Juki HZL-400. I love them both! Anyways, just wanted to give you a lil more info. You can do a search here on QB on all the machines you're interested in, too..there's a lot of helpful posts from others who wanted info before they bought their machines.
Good luck with your decision, and let us know what you pick!
Regards,
Kif