A few people had suggested it in the Sapphire 875's stead, and when we went to speak to my local Janome dealer, even he suggested the 6600 over the 875 without any input from me.
We spoke with him for a while, I read reviews when I got home... I think my decision's made.
I already have a Janome so I wouldn't need to buy all new bobbins etc. And the 6600 comes with the feet I need. With the 875 I'd need to buy the extra feet, at an exorbitant price at that.
The only thing I'm pondering, and it's only a little thing, is whether the extra one inch on the 875's throat is going to make a big difference. Probably not, right? The guy did say Janome's releasing an 11" throat machine in May, but the cost doubles. So no thanks.
Anyway I shall think on it, save my pennies and hopefully sometime soon I can upgrade my machine!