Seek, you want "exactly", but definitions of mid-bass can vary. The 60-120Hz octave would be fairly representative. Some might start it at 80Hz. My M22s(when used without a sub)provide quite strong response in that range and I certainly wouldn't want more mid-bass. More isn't necessarily better.
As to power conditioners, competently designed audio equipment "conditions" the power coming out of the wall outlet by using the transformer, rectifier and filter capacitors in the power supply section. Clean DC is supplied for amplification. No further conditioning is needed and I've never used any.
