I hear no grain on the FPB in my system and Knghifi that is why your sound was dark because of the MIT. I always hear this with MIT and the other company.Probably your system is MUCH SUPERIOR to my pre Agon OLD system :-) I'm sure quality of associated components contributed to the graininess.
I demoed many cables and found either lacking bass or too bright. At the time top of line MIT worked best. I sold MITs after the Krell.