i have the 6600 as well, and also bought mine second hand from the dealer (so it came with a warranty). Love the machine *now*. Every other sewing machine I've owned or used I just sat down and everything was roses ... the Janome for some reason took some time before we got used to each other - both piecing and FMQ.
I LOVE the machine for FMQ, and I love it for piecing strips - the accufeed really comes in handy for that!!
Check with your dealer to see if they have any used machines. Chances are pretty good they will because Janome recently came out with a newer, bigger, more bells-and-whistles machine so some people may have traded in their 6600 or 7700 for the new one. I got my 6600 when the 7700 came out and folks traded up.