My vote is Fitz.  Said it a few times on the forums, terrible KC D, Fitz is on fire, Bills D is terrible so not like Bills can take a lead and sit on their D.
If its between guys in topic, then Stafford for me, best long-term value.  If just this week, then Kitna please.  The jags are god awful as well, and Dallas has a lot of toys.
I like Cassel too, dont get me wrong, but Bills are actually top 10 in passing yards against.  I know, its shocking!! But not as shocking when you realize they are DEAD LAST in rushing yards against at a WHOPPING 174.5 ypg.  I could see KC just pounding that ball all day.  And if they get a lead early, they may never have to pass.