I have not heard the The TU-8200. I have heard the TU-8600 (300B amp) and it is a terrific amp for the money. I am a fan of the 6L6 tube, so I would bet that the TU-8200 is a winner. I hope you find something that it will drive to a satisfying level.
From my experience, the kind of music that is hardest to achieve a satisfying or realistic listening level with low-powered amps is choral music, particularly acapella choral music. At surprisingly soft subjective levels, the music seems to fall apart.
You are probably on the right track looking at Zu speakers--they are fairly efficient and easy to drive. Zu's are very punchy sounding speakers; for some reason, the Zu representatives show them only with solid state amps, so I have not heard them used with low-powered tube gear. Audio Note AN-K are nice speakers that are also not crazy expensive (they are warmer and more relaxed sounding than Zu speakers); I've heard them with fairly low-powered SET amps (7.5 watts/channel) and with push-pull 6L6 amps and they sound good.
I have much preferred Lowther drivers used as wide range drivers (used as a midrange), rather than as a full range driver, but, they can be terrific as fullrange drivers in back-loaded horn systems.