The BIG problem with 45 SET amps is finding the right speaker. Those that can deliver close to a full range sound at reasonably high volume level and with decent tonal balance are primarily giant horn-loaded systems. The trade-off is very high price, and having to place a very large system in an appropriate space. If that trade-off is not feasible, one has to live with volume limitations when using moderately efficient speakers or the tonal quirks of some high-efficiency alternatives like single driver systems. I have found such systems to be interesting, but, too colored and too restricted in both top and bottom frequency response to be usable with all kinds of music.
I bring this up because I have, since this thread ended a few years ago, heard some notable exceptions. The single driver, back-loaded horn systems by Charney Audio are very good all around speakers, capable of playing all sorts of music, and they are quite efficient. I heard them working with SET 300b amps. They come with various choices for the single driver. I particularly liked the one with the AER driver. For a much lower price point, I like the Rethm Bhaava. This uses a high efficiency full range driver to cover the upper bass to treble range and has a built-in powered woofer to handle the low end. Like the Charney speakers, these are compact systems that can work in a large variety of rooms.
I bring this up because I have, since this thread ended a few years ago, heard some notable exceptions. The single driver, back-loaded horn systems by Charney Audio are very good all around speakers, capable of playing all sorts of music, and they are quite efficient. I heard them working with SET 300b amps. They come with various choices for the single driver. I particularly liked the one with the AER driver. For a much lower price point, I like the Rethm Bhaava. This uses a high efficiency full range driver to cover the upper bass to treble range and has a built-in powered woofer to handle the low end. Like the Charney speakers, these are compact systems that can work in a large variety of rooms.