8 ohm speaker in 4 ohm SS amp?

[Mike Sulzer]

If you need to wring every last possible watt out of the amp, then go to the 4 ohm.
I gather that is what you want when you say 'cleanest power possible'.
On the other hand, if it's that critical, why not add another 8 ohm cab in parallel which will give you even more SPL gain due to the extra speaker.

But is he just interested in on axis?