The speakers are easily refurbished (I'd say a recap and tweeter service are in order). Same with the 800. I can't quote prices for all of that as I serviced all of my speakers myself but there are some VERY talented and reasonably priced options on this forum.

6k's are end-game speakers unless you jump into the more recent 8k's - which for me is a few tax brackets up market. 861 is the same idea. There really isn't anywhere to go other than jumping to outside of Meridian (is Trinnov still the go-to?).

So you've got quite the baseline there. I would say that the center is the only thing lacking in that rig. The 5kC is excellent in a 5k setup but it can't fill in like a 55kC or similar size class.

What are your plans? Refurbish? Either way I can only imagine your excitement when you found those things!

main room: 861v4, 2x6000L/R (24/96) 1x5500HC (24/96), 2x DSP33(Rears)
MS200/Roon, 598, Revox b710mkII tape deck, Revox b760 FM tuner, Revox b790 turntable
bedroom: 568.2mm, 3x5000(LCR) (24/96)