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?
Ok, here is a question that may show my ignorance of this subject but, I will ask anyway. I have a TAD-60 AMP (60 WPC ultralinear).. It has 8 and 4 ohm terminals. I am running Vandersteen 2CE signatures which are rated at 7 ohms nominal and 4 ohms minimum. I am currently using the 8 ohm terminals in my set up. Would I be better off using the 4 ohm terminals? If so, then why. If not then why not.

A simplified response -

If bass control seems to be a problem for you when you use the 8 ohm taps use the 4 ohm taps. If you use the 4ohm taps and the highs are not smooth use the 8 ohm taps.

Simply said, use the taps which sound best to you. My guess is that if you are listening at moderate levels the 8 ohm taps might sound best.
Eagleman, feel free to ask w/o feeling you will get criticized. I get snides and insults due to lack of tech knowledge, snotty attitude, "mister-know-it-all", negativity, closed minded-ness. So as long as you don't follow me, you'll do all right here. btw I liked your question and Newbee's appropriate answer. I was not aware of how the 4 ohm and 8 ohm taps respond on different fq's. I still don't grasp ohm idea. Only that 4 ohm draws more volts/current from the tube amp. So it was a good question.
>>I get snides and insults due to lack of tech knowledge, snotty attitude, "mister-know-it-all", negativity, closed minded-ness<<

You make stupid statements.

If you open the door, people will walk in.
The point of the topic was to ask the GENERALIZED question that tube amps prefer 8 ohm speakers(though even 8 ohm speakers can dip to 4 ohms on huge orchestral challenges).

The answer to that is 'yes!', regardless of the tube amplifier technology.

The 4 ohm taps on almost all output transformers (excepting those that the 4 ohm tap is the *highest* tap). perform to a lower level than the other taps. The loss in bandwidth and increase in distortion is readily measurable and audible.

IOW: "Anytime you are investing in tube amplifier technology, that investment will be best served by a speaker that is 8 ohms or more, all other things being equal."