How hot is hot when moving from class a/b to to a or tubes?

Where to even begin…. All of your responses have been really helpful. Massively appreciate the time taken and passion for the subject. 
 

I have take all your suggestions and will start my research for my new purchase. 
 

Thanks again. 

Not hot at all for the amp you need to drive those speakers.

I have 5 tube amps. The smallest ones, 2 wpc EL84, is about 60 watts. My 300b is 150watts, my push pull KT66 is 180 watts. none of those heat up the room. these are measured numbers which are always much lower than nameplate numbers. Most people don’t understand this.

My push pull 6c33c is 400 watts. It does heat up the room.

You need 2 watts. make sure you choose a DHT SET or at least audition one.

Jerry

I have the L-509x and Luxman USA confirmed that the L-509x operates as Class A up to 6 watts, then transitions to A/B.

With high efficiency speakers and modest listening levels, the L-509x likely operates solely in Class A.

My Pass XA25 gets warm. I could not say it gets hot. Even when left on several days.  Pure class A 25wpc. More than enough power for the Zu speaker.

I would be wanting to try a tube SET amplifier if I owned those speakers.

Wonderfully efficient speakers with the Zu.  I have efficient speakers that I run and have been running a Decware SE34I.  The 6 watts/channel is more than adequate.  This runs a pentode tube, the EL34, as a single ended triode.  You will notice a few things about Decware right away.  First and foremost, you can talk to their creator Steve Deckart about any concerns and what you are trying to accomplish.  They are hardly ever available on the secondary market.  I believe people buy and keep.  That is certainly my plan.  Another nasty aspect is you are going to be waiting about a year, if you order.  As to heat, there is some but not a furnace.  As to longevity tube amps and their assembly are almost always fixable.  I have a Dynaco ST-70 that is from the early 60's.  The Dynaco does run warmer than the Decware and the Dynaco has a cage cover.  I have had the Dynaco recapped once and new tubes probably 4-5 times.  I do have to bias the Dynaco occasionally but the Decware is self biasing.  I also have a Audio Research amp that requires biasing.  Self biasing is nice.  You can also get into the fun habit of tube rolling.  It does take some time to warm up.  It sounds good, and is ready to go about 2 minutes after fire up but gets to sounding better after a 1/2 hour or so.  That said, I have an old Threshold Cas2 amp, solid state, that takes an hour or more to find true sweetness.