efficiency- hope i spelt that wright.

Is a guy wasting his money buying inefficient speakers?

No. There is a lot more to speakers than this. Distortion. Dispersion. Driver integration. Compression. I have heard 83 db sensitivity speakers that play much louder than 91 db sensitivity speakers even if you drive the 91 db speakers with the same powerful amp that the 83 db speakers demand....a lot depends on Xmax and thermal compression. Many high sensitivity speakers with very light weight cones and long voice coils in small magnetic gaps (aka cheap drivers) will distort and compress very quickly.

"the lower the wattage, the cheaper the amp" is way off line. I'd take a 7 watt 300B tube amp over a 200 watt mass production solid state amp any day. The 300B is probably more money too. Quality, not quantity!

I agree with Elvick...quality first, however, if you do go with a mere 7 watts then you definitely need a highly efficient speaker...an 83 db speaker will be severely restricted if driven by 7 watts....in that case you might consider horns as an excellent match.

In addition to what's stated above about efficiency and impedance speakers with exceedingly complex crossover design, i.e. Wilson, will be intrinsically harder to drive no matter how forgiving the other specs. That's why speakers such as Reference 3A are so easy to drive with low-power amps, the crossover is a single capacitor, so power transfer is ultra efficient.

Magnus, a speaker should always be viewed in relation to what amplifier it would be used with.

If you have a low output (low wattage) amplifier, especially the vacuum tubed variety, you would want to use a fairly efficient speaker with high(ish) impedance rating and benign impedance curve.

If you have a huge, high watt solid state amplifier, you would normally want a less efficient speaker with a lower impedance rating. Very efficient speakers on big amps sometimes result in a audible hiss. (Note, I said sometimes, not always). Low efficiency speakers go a long way to hide amplifier and line noise.

You’ll find that many very efficient speaker are expensive, and it normally works out cheaper to purchase a bigger amp with less costly less efficient speakers.

Low output amps are also not always cheaper. Many single digit output tube amps can retail for many tens of thousands of dollars. Price of the amp is determined by a number of factors, not always simply on output.

Regards
Paul