How much power needed to drive 91db speakers?

I think that evaluating specs is an exercise in futility. I had an integrated specced at 300w @8ohm and then moved up to separates with an identically specced amp. The separate amp must be making twice the actual power of the identically specced integrated. Get some gear into your room and trust your ears. I don't trust the measured specs.

My room is X feet long and Y feet wide and Z feet high.  What color should I paint it for best sound?  Pretty absurd question right?  Please try to think before you post.  Ask yourself what is it you really seek to learn.

You get 91dB @ 1m from 2W.  It will drop by 6dB at double distance resulting in 79dB @ 4m.  Presence of the second speaker and room reflections add 3dB each resulting in 85dB.   20W of power will produce sufficient 95dB loudness (85dB+10dB).

@kofibaffour 

Opting for a tube amp is hardly “crippling” oneself.

I regularly drive a pair of JBL 4349s (91dB) with either a Sugden A21 SE Signature (30W class-A solid state) an an AR i/50 (50W push-pull tube, class AB). No issues with either having plenty of power.