Just buy the nad and forget about it. It has way more then enough power to drive whatever speakers you got anyway.

Just think of it like a Mcintosh. Right now i have a MC250 im burining in, Its rated at 50 wpc. Into 4 8 or 16 ohms.. It uses an autoformer system to impedance match the speaker load to the transistors for maximim power transfer.

Haoleb's Audio/DIY Website