Hi pacifico,
Many thanks for your post.
I really feel the new M5 would be the right choice. It mates up extremely well with SS amps and I have a NAD integrated and the synergy is great. I did design them with SS in mind and have tried numerous amps with them. The digital amps are excellent too.
With tube amps I would go with higher power. Not recommended for 2A3s. 300B and up would be good. I like PP EL-84 and EL-34s with them.
Thanks gain,
Louis