Just a quick advice, I have been down a similar road though for different reasons. I would be extremely careful with mixing 18 bit and 24 bit speakers. It is a hazardous road and there are inevitable compromises, and inevitably unexpected additional expense to solve.

I finally did not solve it until I switched my entire array to 24 bit, 7k's on the front a 5k smiley face centre and black ash converted 5k's on the rear. I also have a 1600 subwoofer which to be honest with the 7k's is is somewhat superfluous. The controller is a G61R.

My second room set up, is now also 24 bit, prior I had a lot of well known problems. The controller is a G91A.

My third room has my old 18 bit 5ks an centre for music only, they are 16 years old and sound perfect, with a 562 and 565.

Happy to tell you more by PM or telephone.

Regards
Huw

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