Q9550 Stepping Question

Hi guys, still kinda new to this and was doing some searching but couldn't find any relevant information. My question is; does E0 vs. C1 stepping really make that much of a difference in my attempts to get my 9550 to 4.0? I know with E0 it will probably do it with less voltage and therefore lower temps but is that the only difference? Also, is there any way to tell the stepping of the processor on the packaging? Thanks