SOM,
Sorry for the delayed response. First, I'd pay close attention to the comments/threads brought up on the Hornshoppe forum. Beyond the tube amps, they're always the ever-changing T-amps to consider. I had someone of Ed's forum build me one based on the 41 hz design and was really blown away by the sonics.
Now, there is something to be said w/the tube amp in the chain but it all depends what you listen to. If you need power, clarity, high VOLUME...I'd consider a t amp w/the speakers. If you listen to a ton of jazz, LPs, etc...go tube.
Plus Ed now offers the "magic cube" bass augmenter as a low end supplement.
Good luck.
C Evans