Luxman M-10X Stereo vs. Mono or C900U


Anyone with the M10X can quantify the difference in stereo mode vs. monoral  mode? 
I currently have a Lumin T2 which I can use to connect directly to M-10X and use it as a preamp. The speakers are Kef Blade One Meta.  Is it better to put the money toward a second M-10X and run them in mono than getting a proper preamp C900U? 

thisisme

do these luxman stereo  amps, when you bridge them into a monoblock 

 

does luxman bridge in series or in parallel

 

are there any measurements online where someone compares the impedance load when bridged ?

Hello

what is the break-in period for the C10X?

which are the main steps? after 50 hours, 100 hours, 200 hours?..etc

thank you

philippe