which tubes for which genre ?

For rock, I would recommend KT88's in push pull.

This will give an easy 30+ watts clean.

KT88's give a very linear uncolored sound.

John C.

I agree that a higher powered push pull amp like vtl,manley
audio research,quicksilver and cary would be my choice for this speaker;but if you can $$ a atmasphere ma1 or ma2 I would look at those as well.
If you able to audition amps in your area I would listen to all that you can; how big your room is will be a important factor as well.

What amp do you currently use to drive the Dynaudios? I share the skepticism of some who have posted responses to you -- if you want to rock, I don't see why you're thinking of tubes. I've owned a variety of tube amps and preamps -- Conrad-Johnson, Quicksilver, Primaluna, Audio Research, Eastern Electric, etc. They all had their attractions, but since picking up a Naim Nait 5i integrated a few years ago, I've had no desire to go back to tubes (which can demand a lot of care and feeding, esp the power amps). But I have a small room and mainly listen to jazz and classical, not rock, so your experience may vary. I still think it's worth thinking twice about WHY you want to go tube -- what goal are you trying to achieve? There may be a better means to the end you seek.

Just to follow up on my previous post -- if you are a complete newbie to tubes, and you just want to try them (a perfectly reasonable desire), then you might want to go with an integrated like the Primaluna Prologue 2. It's pretty much plug-and-play, with its auto-bias feature. And it allows you to use various power tubes, so you can compare, for example, KT-88s and EL-34s. You can do a little tube rolling with the small tubes as well to tailor the sound to your liking. I owned the Primaluna for a while and liked it, and unlike some other tube gear I've owned, it always behaved well, never needed fixing.

Another possible combination for you -- a tube preamp and a solid-state power amp. One of my favorite combos from the past was a Conrad-Johnson PV12L tube preamp driving a McCormack DNA-125 power amp -- grace, warmth, and muscle.

15465550, the Audience 42 is built for transistor amps in an attempt to get more power into the speaker without affecting its apparent sensitivity. But the speaker can be driven successfully with tubes, and while you will need some power, you do not need a power house amplifier- much more than 150 watts and you can damage the speaker.

I would recommend something that has at least 60 watts or so. Some tube amps will drive the speaker very well directly, but IME many tube amps do have troubles with 4 ohms, so my recommendation is to also consider using a set of ZEROs (see http://www.zeroimpedance.com).

If you do this properly, you will find the bass of a good tube amp to be actually better than that of most transistor amps.