I think it's a mistake to plan on clipping, even if it's mostly 2d harmonic. An amp that's clipping a your listening levels likely has very high distortion, particularly in the bass and highs. This should be avoided if you want accurate musical presentation.
I agree with you Dave...but one has to respect that many people don't want an accurate presentation - they prefer even order harmonic distortion from soft clipping. I think of the excellent Sonic Frontiers manual about "A taste of Tubes"....that is what it is about....adding your own seasoning to your favorite tracks. Judicious use of the volume control allows a user to control the amount of soft clipping to achieve a desired effect....it is a form of audio compression similar to what is done in studios.