I was just in the same situation...and ended up purchasing a DX7.  The extra channel was too much to pass up.  I'm not sure how good of a deal it was (or wasn't), but I got the DX7 and a AR6200 for $274 (no tax or shipping).  I would hate to need that 7th channel anytime soon and not have it (I'd like to do flaps and lights)...and it felt a bit better (heavier, really).