I have the 6600P and love it. I did not need the extra "blue dot" bobbin case for FMQ .. no problems. So you might want to try without it first and spend the $$ on a 1/4" accufeed foot
I piece everything with my 1/4" accufeed foot (except of course paper piecing).
If you are on a budget and the new retail price is just out of range but your heart is set on this machine ... ask the dealer if they have a used 6600P available. That's how I got mine. I really liked the machine but because I had a fairly new Husqvarna 535 I couldn't justify spending over $1,000 on yet another new machine. Picked mine up for $700 and it included all the feet that usually come with the machine, the extension table, the knee lift, and the soft cover - and it included a 90 day warranty. The dealer had taken it in as a trade in when the 7700 came out, serviced it, and sold it. Since Janome has recently released another new machine, there is a good chance that they have a trade-in 6600 .. or perhaps even 7700 at reasonable prices. Have not had a single problem with mine ... had it 4 years now.