They aren't many iPod Docks with tube amplifier on the market but this one from Dice will enjoy you.

The iTPA-220 is a nice amplifier delivering 2x20W that will give you a warm analog sound with its tubes (2x 6N3 tube). The dock includes an iPod charging function, a video output hooked up from the iPod for playing video on a TV for example. Also an auxiliary input has been added for playing additional audio devices such as computers, non-Apple MP3 players and so on.

The speakers are constructed in a bass-reflex wooden cabinet for better sound reproduction with inside a 4" mid/bass driver and 1" dome tweeter for full dynamic range.

The iTPA-220 costs $299 and won't be available until September, but you can pre-order it on Dice Electronics website now.