Tube amps and speaker ohms

In your opinion , do push pull amps work better with 8 ohms or 4 ohms. .I am under the impression the lower the ohms, the more power is demanded from the amp....Another question, are there low powered SET amps ,and high power SET amps?
I'm looking at a 40 watt 845 tube amp for my 8 ohm, 89 db speaker.. just cked the Thor has a 86 db W18 midwoofers(2 per cabinet) and a 88 db tweeter. Will an 845 amp rated 40 watts be able to drive the 86/88 db speaker? With authority, bass, mids, highs, in dynamic sound stage? Synergy? Or poor match?
David, the best advice I can give you is to talk to a few speaker builders/manufacturers. They will be able to give you very good advice. There a couple on the BB like Audiokinesis who I am sure will be happy to talk to you. A few others are omega, decware, coincident etc.

I have speakers rated at 88db/1watt/1mtr sensitivity that I drive to very loud levels with a 12wpc tube amp. The bass really pounds and I can measure it down to the mid 20’s (albeit at –10db). I can do that only because my speakers are very tube friendly. Some other poster mentioned his 200wpc amp is barely capable with 96db rated speakers – somewhat ridiculous no? If I hook up my 22wpc SET I can blast the doors down.

Dear Bartokfan: The speaker efficiency ( 86db,89db,etc )is not the only subject when you want to choose an amplifier, either the nominal speaker impedance ( 8 Ohms, 4 Ohms, etc, etc ) because what you need to know is not only the nominqal impedance but the electrical curve speaker impedance where you can " see " how low goes that impedance.

The other critical subject that you have to take in count is the output amplifier impedance that IMHO must be a low one: say below 0.1 Ohm.

Regards and enjoy the music.
raul. i googled amplifier output impedance and got several hits. The info if over my understanding, but will try to work with the ideas. I grasp that quality of transformers is vital in tube design, especially when driving a devil of a speaker such as are the Seas Excel. The motor on these speakers causes havoc on most tube amps. I assume.
Lets see if this link loads:
Dear bartokfan: +++++ " This is the way loudspeakers behave. Loudspeakers are not constant power devices. Loudspeakers must have a constant drive voltage to provide a constant acoustic output with changing frequency. As demonstrated by the simple mathematical relationships shown above, the only way to achieve constant voltage drive with a changing load impedance is by having very low amplifier impedance. " +++++

This is what you can read on the link you posted, as you can " see " this subject is critical.

Now, the tube amplifier technology has many trouble to handle in the right way all those speaker needs, so ( if you want to go with this technology ) you have to make big trade-offs with it.
Of course that you could choose for SS technology that could mate in a better way your speakers needs and your music sound reproduction priorities.

Regards and enjoy the music.