Real life dynamic range of LP vs. CD
The previous poster brought up the old vinyl/CD discussion, which is really a very difficult and subjective topic to discuss about. It's much to do what kind of sound you personally prefer.
Yeah, maybe vinyl theoretical dynamic range is in tune of 120 dB but in reality, according to some randomly selected web pages below, the range is somewhere between 60 and 80 dB:
About valve amps: They are thought to sound musical compared to transistor amplifiers as they add harmonic distortion (normally measured as THD) to the sound, sometimes in the tune of several percent. The distortion is the reason why e.g. violins are made of wood as opposed to concrete.
The added distortion by e.g. valve amplifier, in my opinion, makes the sound less realistic, i.e. LoFi :-) This is especially true when a tube amp is overloaded, which is pretty easy to do as their output power is normally lower than transistor ones. However, human ear finds harmonic distortion pleasant, hence the tube amps sound more "musical". Even badly recored harsh material sounds bearable through tube amp as opposed to a real HiFi amp :-) However, if you material is recorded right you get way more resolution with (a well designed) transistor amp.
There are also other stuff that matters like (normally) less than straight frequency response characteristics etc. but I think this is enough for now.
Tube amps do not care if the incoming signal is digital or analog. They add distortion in both cases. If you like the sound of them I can't see any reason not to connect a iPod to one.
Here's my humble opionion.