The best 5.1 mix of BSS is on the 2000 DVDA from Rhino. It also has a bonus track of Lucky Man in 5.1. It's been a while since I listened to it, but I thought the later Jakko mix was generally pretty good up until the last track. The mix of Karn Evil 9 3rd Impression is unaccountably missing the voice of the computer during the climactic confrontation - you can only hear a very faint echo of it in the other channels - which pretty much destroys the point of the track. That glaring error doesn't reflect well on Jakko and/or whoever was doing QC for that release.
The entire ELP catalog needs to be revisited in Atmos, but only if a good mixing engineer is given a free hand to make their own decisions. Apparently there are a lot of alternate track/takes to choose from.