You will love the 866 and the Rockports….sounds like you were at Soundings in Denver. (The Nordost recommendation). Hopefully you got the digital version of the 866, its quite amazing for the miniscule cost to upgrade. Its the best $20,000 solid state integrated amp in my opinion and it only costs $15,000! I’ve purchased three 866’s from Soundings and Jeff is outstanding. They are a fantastic dealer IMO.
The Rockports are exceptional as well. Ignore those telling you its foolish to spend this much….it isnt if you have it and enjoy music. Its highly likely they havent heard anything of this caliber or they wouldnt have said anything. Reach out to Boulder and ask about speaker cables….its actually the amp that is more particular about cables than speakers but you dont have to go crazy. I found the Tellurium Q Black to be a nice power cable for the 866. Its not that fussy, even a Shunyata would be nice. Boulder and exceptional power supplies are synonomous. Its a dead quiet amp. Might I suggest that you shop used/certified Gen 5 pre owned Transparent speaker cables. Thats probably what is inside your Rockports.
You will love your new setup.