The Cell merely gives devs more options for squeezing out better graphics than the RSX can do on its own, since that's the only real way to even use all of the Cell's SPE's. This isn't something to be impressed by either. Both consoles are definitely completely GPU bound. 3 CPU cores is plenty for a console. Had Sony gone with a more standard 2-3 core CPU, they could have spent more resources on a better GPU which would have had a much larger impact on the PS3's graphical abilities.