A change in efficiency to the final sound


I have a p/p tube amp running a pair of 6Ca7's for about 30 watts per channel .
I have read here that p/p tube amps sound their best when they have to work a bit harder , as opposed to a SET amp that sounds best near idle .
My present speakers are claimed to be 92 db. eff.
If this amp is driving a pair of speakers rated at 85 db. efficiency , should it sound a bit better due to working a little harder or closer to its optimum level ?
Conversely , would the same amp sound a bit worse driving a more efficient speaker of 99 db. due to it working less hard or further away from its optimum level ?


Thank you

saki70
@lowrider57's repost of my quote has made me realize that I should clarify: when I said "the higher the speaker impedance, the lower the distortion", the distortion I was speaking of is that produced by the amplifier, not the loudspeaker.
Maybe I can have some input on this as I'll be added a pair of Maganapan 0.7 speakers in a few weeks to my system. Currently I'm using a VAC PA 80 80 set in triode mode with a ARC LS15 pre amp that drive my Definitive technology Mythos ST speakers that are rated at 91 db efficiency 
The speakers do double duty for me as I also use them for HT. The VAC at 35 watts has no problem driving the Mythos ST's  

I'm very sceptical that the VAC with have enough juice in triode Mode for the Maganpan 0.7's but will give it a try and a good listen. More that likely I'll have to convert the VAC to PP and see if that has the power required. It does have 2,4&8 ohm taps and weights a ton! It should be interesting to listen for any changes in sound quality when it's in PP mode
I wanted to add , in the above supposition , that the volume for each speaker would be the same . This would mean that the amp would be 
barely idling on the 99db. speaker and turned up for the 85 db. speaker .

Would the resulting sound change due to how hard the amp is working 
or would the sound be the same regardless of how hard the amp has to work ?

Thanks again
It will sound different,though I'm not able to explain why.My amp can be switched from push pull to single ended.I can hear a difference.
"If I use this 30 watt p/p tube amp with two different speakers , one with 99db. efficiency and one with 86db. efficiency and all other characteristics being equal , would the amp have a different sound with each ? If so , how ?"

If the listed dB specifications are at 1watt/1meter, then the 99dB speaker will sound louder than the 85dB rated speaker at the same listening distance when fed the same power. This applies to any amplifier regardless of its power rating.