I had the same problem with the tones of these two speakers. In the beginning the tones were completely different. When I purchased the C5, the tweeter was dented and the store did not have a return policy. So I fixed the tweeter myself. Now it is much better but not perfect. Please check if your tweeter is intact.
Thank you for the confirmation. Do you have any suggestion on a power amp which will work well with the B6s.
Thanks for your response. Marantz NR1403 spec calls out for 2.1 pre amplifier out. Please confirm.