I highly recommend the Janome 6600 which you should be able to purchase new to be in your price range. It has the built-in walking foot (called AccuFeed), you can program stitches, it comes with a quilting platform, it has lots and lots of decorative stitching, has lettering, and a knee lift so you can keep both hands on your quilting, but still move the sewing item without letting go of it. I also make lots of bags, and it has absolutely no trouble with heavy duty sewing.
I also have the Janome 7700 and it will do everything the 6600 does, has more decorative stitches, enhanced AccuFeed system and 3 stitches designed specifically for freemotion quilting that convert the normal sewing machine to a quilting machine. It's a bit more than your limit, but this month, Janome was including a sewing table, quilting platform, another lightweight machine, and a thread collection (may be missing something because the deal was really great! wished I'd waited to buy it when the deal came out.)
A great thing about the Janome machines - they usually come with most of the feet we all have to have - and the ones we do buy are usually about half the cost of Bernina or Brother machines.