Class A or not, break-in or not, I'm not sure a Krell would be a good match for B&W either. I barely tolerated the big B&Ws with the big warmer Classes when last auditioned. Stick the M-506 in and take a listen. Don't be hung up on cost.
(For fun, teach your sig-o to change amp connections without you looking... :-)
Gotta believe someone would love those Krells driving warmer, more musical speakers in another system if necessary. All good stuff but maybe not the best synergy as others have suggested.