Those 45W chips are just selected(binned) for lower power consumption at a given frequency.
I tested an BE2400 and 4850e and an 5000BE. At 3.125GHz they all required ~1.475V.
So for overclocking in that price segement the 5000BE is the best way to go due to it's unlocked multi.

@VVJ: Thank's I'll give it a try. I like the power consumption information on CBid.