[snowman_al]

You do not say if this is mono or stereo, hifi or or workshop amp.

Any way, I think you are making it f a r t o o complicated. You can satisfy some of the people some of the time, the more you 'offer' the more likely you are going to fall into a gap.

I agree with Lucien, just focus on the standard low impedance phones (8 - 32Ω). There are too many variables even then...