Classé is a typical match for B&W 802 Diamonds and an obvious choice. It's nice gear and it gets down to personal choice.
If you are going to build a hybrid 2ch/multi-ch system, I think brand synergy is key. You need to decide now what direction to go else you will waste money down the line.
You are weighing up Classé vs McIntosh vs Krell vs Bryston to drive B&W loudspeakers. Consider each brand's product lines and try to visualise the additional components you will be purchasing to build a hybrid 2ch/HT system with a budget in mind. Add 30% to that budget because there are hidden trappings going hybrid multi-ch. You will be building a complex system.
Personally I'm not a fan of Classé being a McIntosh guy. I have a very high regard for Bryston for value and support. I would probably choose Bryston over Classé for the longer term purpose you have in mind.
If I were to suggest a start for you, I would be biased and say go with the McIntosh MC452. A great fully balanced stereo amp. An amp that could be repurposed should you wish to scale up and use it to drive side surrounds in the future. A multi-ch amp will be required either way. That basis would commit you to building a McIntosh rig. If resale or collectibility are also value considerations, McIntosh is renowned for holding greater resale value longer term.