I agree with Rar1, including that Rotel and the B&W 600 series are a good match. The preout on the Rotel could also be used in a bi-amp configuration with the separate RB971 power amp. This is probably a more likely scenario than just using the RA972 as a preamp.
If you are still using cheap cables, then I would start there before thinking of new gear.
If you are still using cheap cables, then I would start there before thinking of new gear.