Added power conditioning:
Most recently I had the Walker Velocitor - had an interesting effect, was way overpriced for the technology inside, and at the end of the day was a major ripoff to anyone who might have bought one brand new. What I learned was that the QRT technology was very effective and I moved in that direction.
Tried a small Silver Circle Audio power block that was not equipped any more inside than the Felix. It was very damaging to the sound, but did help the noise.
I started experimenting with Audio Magic Gen ZX's and PEA's to great effect. I ended up hard wiring a Gen ZX into each monoblock, placed a small PEA over the circuit breaker (highly recommended), and then eventually put a medium PEA over each monoblock's grates as well.
The Kemp QRT's also work very well and are adjustable. The cheapest QRT technology you can buy.
I still have a Running Springs Duke I used on the amps to great effect. I have not tried it in combination with my latest XXX unit from Audio Magic yet.
One thing for sure is that sibilance is completely gone with AM gear and the noise level is significantly reduced. Not 100% gone but way better than prior setups.
Here are some recent photos: