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.