Getting what you paid for your machine four years ago is definitely a good deal!! However, whether the model you are considering is for you or not, is something only you know! Janome has a good site with the ability to compare the features of their different machines.
I have had 3 Janomes and have ben quite happy with them. Add to that a wonderful dealer!! If you're happy with your dealer, that's certainly one reason to stay with them.
As for pricing ... look around and check the price for the same model with other dealers. One way to check your dealer and whether they truly are giving you a deal ... ask them what they would charge if you bought the machine without trading your BL. That might tell you how "real" their price is! After all, you might want to keep it as a 2nd machine, or give it to a family member.
Good Luck!