What amp should I use for the B&W htm2d and scm?

I was going to initially suggest the Classe 3200 amp but that is warmer than your 802D and Byston combo. I have the B&W 803D, HTM2D center, DS8S surrounds and in-ceiling ccm-65 backs and use a Rotel RMB-1095 for the center surrounds and backs.

Absent another Bryston (presuming you like the sound with your 802Ds) I think the RMB-1095 would be sufficent for HT matching and/or all channel stereo duties.

I'm using a Spectron Musician III SE with my 803Ds.

I was using a Krell KAV-3250, sounded great... Unfortunately it broke, and shipped off to repair. To tide me over, I picked up a Rotel RMB-1066, bridged to 150 WPC... To be totally honest, it sounds great too... Is the Krell sound better yes. Does it sound 3K better?? not totally sure...

Typically, you would want an amp that has the same sound signature as your fronts. This way the Center and Rears sound as seemless as possible.

If you are keeping the Bryston on the Fronts, you should stick with a similar sounding Bryston for the other channels.