some say that it sounds warm. i am no expert but for me (on personal experience) id say more detailed, specially on the mids. mas rinig mo ang pluck and strum ng guitars at tining ng piano keys. you will clearly notice the difference, like night and day
it's like opening up the characteristics of your speakers, my bookshelf even became boomy with the 35wpc integrated tube amp. but id also say that it depends on the source you will be using, the type of speakers that you'll be driving and the music that you'll listen to. as everything still has to be appropriate and proportioned for it to have a good and balanced match.
i also think that the tubes power are under rated (or avrs are over rated
)
i also tried using tubes on concert dvds but it did'nt sound good but the best sa cd/dvd audio or mp3 and vinyls.
once you go tube, you'll never go back.