Sorry - I forgot to answer your query about tubes.
Because the impedance is so benign (see the email that I sent to you with the impedance and phase plot of El Diablo) all amplifiers are treated very gently and allowed to perform at their best ... no strain at all.
Depending on the size of your room and how much output you really want from the speaker, Diablo can get to extremely respectable levels with 15-20 high quality tube-watts. In a fairly small room you might even be able to get away with a sub-10-watt amplifier - but don't expect too much from the low frequencies. You may get extension, but you won't get the same kind of control that you'd get from a 100-watt Push Pull ...
Because the impedance is so benign (see the email that I sent to you with the impedance and phase plot of El Diablo) all amplifiers are treated very gently and allowed to perform at their best ... no strain at all.
Depending on the size of your room and how much output you really want from the speaker, Diablo can get to extremely respectable levels with 15-20 high quality tube-watts. In a fairly small room you might even be able to get away with a sub-10-watt amplifier - but don't expect too much from the low frequencies. You may get extension, but you won't get the same kind of control that you'd get from a 100-watt Push Pull ...