In other words, if you get a cheaper CPU with a low (and locked) multiplier, you may not be able to reach the max overclock the chip could otherwise. Also you are gonna have to mess around with ram dividier / NB clock a bit harder compared to on a BE cpu.
There are three different steppings out now: C2, C3 and E0. You can find the detailed information on this at wikipedia (list of phenom II processors or something along that line). Though each chip varies in overclockability, C2 tends to be hotter and has trouble reaching 4ghz on air in most cases. C3 is somewhat better, and E0 should be better yet although they are still too young to be judged. E0s are only found in thubans currently (zosmas aint' available yet).
The debate over dual vs quads for gaming isn't over yet. If you ask me personally, I would have to say anything over 3ghz dual core would be mostly sufficient, not to mention chances of successful deneb core unlocking is quite high. Thuban would be nice for encoding and such, but for a gamer money would be better spent on a good GPU.
Just picked up a phII 555BE cpu/mobo combo for $90AR + tax over the weekend, unlocked it to quad core