If you plan to keep the B&Ws, the Ayre is likely one of the better choices. This speaker does not play well with tubes due to the nature of its load (4 ohms in the bass, 8 ohms in the mids and highs). Four ohm loads should be avoided with tube amps even if they have a 4 ohm tap- almost any output transformer will loose a good octave of bandwidth off of the bottom end, simply by going for 8 to 4 ohms and the distortion is usually higher.
If you really want serve your amplifier investment dollar, the speaker should be either 8 or 16 ohms for best results! Even if you have a transistor amp, if sound **quality** is your goal, you will do better with a higher impedance speaker as the amp will make less distortion (read: smoother, more transparent). If sound pressure is your goal, there is a slight advantage to four ohm speakers, assuming the efficiency is otherwise the same.
If you really want serve your amplifier investment dollar, the speaker should be either 8 or 16 ohms for best results! Even if you have a transistor amp, if sound **quality** is your goal, you will do better with a higher impedance speaker as the amp will make less distortion (read: smoother, more transparent). If sound pressure is your goal, there is a slight advantage to four ohm speakers, assuming the efficiency is otherwise the same.