EL34 tube monoblocks that doubles power at 4 ohms

What you`re seeking is`nt a characteristic of tubes.This quality is offered by some solid state designs. This does`nt ensure better sound necessarily in all circumstances.Really depends on the speaker being driven.
Regards,

I agree and emphasize that tube power actually seems to increase against higher impedance loads not the other way around. I understand that this is a lack of higher current being made on demand by tubes in that face of low impedance. If you want more watts output then you need more tubes and overall bigger tube amps to get that. This is one of tube's limitations, which in my mind are made up for by the imagery and tone tubes are capable of. I have not heard with SS amps that equal it. Some fine SS amps do image pretty well but not to the extent a tube power amp does.

Tube amps with output transformers have taps for correct connection to your speaker each tap will put out the same power. Good tube amps have large and stiff power supplies so the doubling is not really necessary.
Alan

Good point -why double if the base line wattage is sufficient?

You might want to take a look at this:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php