Boulder 866 / Rotel Michi M8

How big is the listening room? How loud do you listen (measured with SPL meter or smartphone app)? This will play into how much power you need.

I’d also call Boulder and get their take on the 866 and 802D3 pairing.  
If it all checks out and I had to purchase without being able to audition, I’d start with a used Boulder 866. 
 

Within the integrated amps space I would also consider CODA CSiB V2 or V3, McIntosh MA9500 and Pass Int250. They all sound different so read up and determine what might work best based on sound characteristics. 

I am still extremely interested in the 866 and the Boulder sound, but there was an unmissable deal, so I currently have new michi M8s. I started burning them in, it was written on the forum that it takes up to 400 hours to burn them in.

If they don't agree, I'll move on.

Rolee, how do you like the M8's? Or did you off them?

They've been working fine for a while now. I got an Esoteric N 05XD while driving, and Esoteric K 05 X as a backup. They make a perfect combo with the B&W 802d3. 
soaring, detailed, dynamic, powerful, airy, fast, and nowhere is it offensive but the character is very fresh, and most importantly, very natural. 

In my system the M8's lacked detail and dimensionality. They reminded me of PS Audio BHK 300s.