I found the original EL34's in the HP Mono Blocks I use were missing too much. I am driving ATC SCM19s that have a flat impedance curve with very little damping problems. I skipped the lesser tubes when I decided to roll and went directly to KT150s. What a difference! They've been in there going on six years and still sound fine.
After I finally got the speakers positioned properly the bass is crisp and fully present. Full disclosure: I added two REL T/7i subs to pick up the very low end that the SCM-19s don't extend to.
Rock, Jazz, Big Band, Blues, Reggae, Zydeco, Female and Male Vocals are all tonally balanced. I've heard a lot of live music and this setup does an excellent reproduction. Plenty of bass.