Jérôme, my Prima Luna DiaLogue One integrated amp originally came with EL34's. I fell head over heels for it after I got used to the resulting change compared to my previous amplifier (a Marantz receiver, actually) and absolutely loved the purity, warmth and romanticism of its sound, specially with vocals, as you pointed out, and strings. I never heard a cello more beautifully reproduced.
Unfortunately, my speakers are not the most sensitive, and I had issues with clipping during some very complex and highly dynamic passages. I needed just a little bit more grunt and bite, and switched to Gold Lions KT88's, which provided that in spades, and then some. A profound change indeed, and the synergy in my system appears to be optimal now. However, from time to time, I do miss that "glow" and lustful midrange that the EL34's gave me... It seems that in our hobby you can rarely have it all!
