MC901 monoblock tube matching Q

Answer A:  Call the manufacturer and ask. 

Answer B:  If you can find a schematic, look at the tubes in a series stack or parallel stack and match those.   In general, you want the gain tubes to be as low noise as possible, so spend a few extra dollars and get super low noise tubes.   You won't need to match between amps, just match tubes within one amp.

Wow, that is quite an amp. Most tube retailers provide matched sets of tubes for no additional cost or a small fee. So why not get matched sets? Not sure what that amp really needs the manual says have your dealer replace the tubes, no help there but the power tubes are run by sophisticated electronics so it's probably one of those that doesn't require matched tubes but that is just a guess.  

This is totally obvious, but at $35K MSRP for the monoblocks be totally sure to get expert advice before retubing these beasts.  It's interesting, I did not realize that there were any combination solid state/tube amplifiers built.