I got the Z40+ integrated to drive Spatial Audio Labs X5s which are also highly efficient speakers.
I bought the LTA (used) because LTA often is paired with the Spatial Audio Lab speakers at shows along with some other accessories.
The first thing I noticed is how clear and fast the Z40+ was with tight bass. I had a tube integrated which I thought was pretty good but this was next level.
The second thing I noticed was that the Z40+ integrated sounded more SS than tube. I changed all of the tubes but probably only needed to change the tubes in the preamp section and got what I was looking for.
Right now, I have what I'm looking for and love the sound. However, I am going to experiment with a Class D GaNfet stereo amp and try to find a tube preamp. The only reason is that on Audiocircle, this amp has been getting raves and, if it is truly as good as the LTA Z40+ integrated (with a decent preamp), it would be significantly cheaper.
Hate to be that guy who adds another option but this is something I'm thinking about even though I am extremely happy with what I have.
https://www.audiocircle.com/index.php?topic=183099.0