Which amp for B&W 805 D3 and HTM2 D3 speakers - Rotel RMB-1555?

I am setting up a system with L&R of 805D3 and Center of HTM2 D3. My understanding is that just the receiver (plan on getting Onkyo TX-RZ50) will not power these speakers well enough to get the most out of their potential. I am thus considering adding a Rotel RMB-1555 for the LCR. I would maybe consider bi-amping L&R since RMB-1555 is 5 channel. My question is whether the RMB-1555 (120W x 5) is sufficient or would there be a significant improvement in going to RMB-1585 (200W x 5). I do not listen to the music too loud. Just want clarity. Per B&W, the recommended amp for 805 D3 is 50W - 120W into 8Ω on unclipped program.

While you are advising me on RMB 1555 vs 1585 for this set-up, I am open to other options in the price range as well.

Thanks