Tube amp and speaker impedence matching

Europas are 4 to 5 Ohms for most of the audible band- no lower than 4 Ohms. Very resistive load, and very little back-emf from them makes your power just fine, in my experience- loud enough to have to turn it down to converse in any room smaller than 600 sq. ft, even on recordings with very high peak-to-average levels.
Best,
Roy Johnson
Green Mountain Audio

I guess impedence is the 'dirty little secret' of the speaker manufacturers. I own Martin Logan Aerius i's which are rated at 4 Ohms (Nominal- that's the White Lie), but the actual impedence drops down to 1.8-ish in the upper high frequency area!! Requested ML to provide the impedence curves and they gracefully declined.

Cdilascia, for being new to this you are pretty smart to catch on to this concern so early in the game. I didn't figure it out until after making some poor purchase choices, but now this is one of the spec areas that I actually pay close attention to in speaker and amp reviews and spec sheets. But often the warnings given are vague: "The MamaMia speaker loading drops down to X.x Ohms below 125 Hz -- be sure and match amplifier carefully!" It's great that I know to be "careful" if considering the MamaMia speaker, but not quite great enough because I don't know exactly what precise values I need to look for in a partnering amp to achieve a good working combination.

Let's say that I get the preference of the speaker manufacturer for which amps are well-suited to drive his speakers, but for whatever reason, I don't like the suggested gear and want to consider other offerings. Does anyone know of a good set of reference tables available which match various speaker parameters with good and bad parameters for amplifiers? Or should we just find a trusted EE friend every time we want to be sure, and feed him whatever specifics the companies (except, apparently, ML) will provide us?

If you really like a speaker that has too low an impedance, I have a couple amps that handle as low as 1.2 ohms with 120 watts-tubes. Let me know if you need new amp suggestions. You can sell the CJ easily.

Thanks for the complement Brett44! And thanks to everyone who has responded, including Roy. I have learned a great deal and the information has truly helped me make a sound decision. Elevick, I'll let you know after I have spent some time with the CAV 50.