$8k for speakers - new or used

You describe "wanting more - maybe detail, punch, bass." Have you considered keeping the B&W's and look into getting a quality subwoofer? You could buy a Rel No. 31 or 32, or a Martin Logan Balanced Force 212 with that budget.

https://rel.net/product-category/reference-series/

https://www.martinlogan.com/en/product/balancedforce-212

Opinions are like..... For my money, I'd ditch Macintosh because AFAIK all their gear is "warm" lacking detail. I'd go open baffle, Caladan, and if you want to better them, PureAudioProject, or the like. Caladans sound pretty bad for the first 300 hours or so, the capacitors are the biggest issue, but the bass drivers definitely improve as well, but they are punishingly bright at first, though perhaps not with a Mac preamp??? 

https://www.audiogon.com/listings/lisbad50-linkwitz-lab-orion-v2-full-range?refsource=hifishark

Revel Salon 2s or Joseph Audio Perspective Graphene, both can be found used right now for $8K to $9K

QLN are very nice, Joseph Audio’s another good one, there’s a lot of good speakers out there, you have a nice budget for used.