$8k for speakers - new or used

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. 

I still have a pair of the original 804's purchased back at the end of 2002.  They still sound quite good, and they are now a part of my Son's system.  Like all 3-way loudspeakers, they require optimal placement.

With the refinements in the D4 model, they should be fantastic.  In my setup, I never required much toe-in.  You may have to experiment with moving them away from the back and side walls.

I have moved on to a smaller home and a 2-way stand mount loudspeaker from Wilson Benesch.  They are matched the W-B Torus system.  Don't give up on the 804 D4's.

I might suggest a different tube preamplifier.  Have a look at the Quicksilver Audio Line Stage offering: https://quicksilveraudio.com/products/line-stage-preamp/

Happy listening