I think all Janome machines are good. Of course, the more you pay, the more features you get, but they all sew good stitches. The 6300 is a larger bed machine with fewer features than the 6500 or 6600, but otherwise it is the same basic machine.
I sold my 6500 for $650 a few months ago, which I felt was a very good deal for the buyer. Sears Kenmore machines used to be made by Janome (those with the 385 prefix in the model number). They are very good machines as well. They are still sold, I suppose until stock runs out, by someone......Allbrands maybe. All of these can be found on Craigslist occasionally...and don't be afraid to offer less.