Give this a try for 30 days and return if you do not like it, the Benchmark LA4 preamp at $2500.
I have one in my office system with AHB2 mono amps and it is my favorite preamp from the many preamps that came through the system in the past 2 years.
I was considering getting the Luxman M-10X amp for my upcoming KEF Blade 2 Meta. However, I narrowed it down to a KRELL or CODA amp instead (owned both lower end models before). With either of these new amps I will buy a second LA4 preamp.
I have heard the Luxman C900u preamp with the Luxman m900u amps and loved the amps, but was not interested in the preamp. I do not want a preamp to add to the sound of the system.