I just talked to the guys at KEF for a good 20 min on the phone. Super helpful, but still haven't really made up my mind which way to go. He says the R100 is still a better speaker than the new Q150, but how much better probably depends on a number of factors: room, gear, source etc. He also said no problem using a Q150 or 350 on its side as a center, but the 650c or 200c are still better for center channel use.
That said, he did suggest the Q350 over the R100 for my room size and use. However, I'm still somewhat skeptical as the Q150 sounds great to me, and any issues with dialogue I have with it now would certainly be cleared up by adding a center channel, so in order to keep it as compact as possible, I'm really leaning towards the R100s with an R200c. More compact, better tweeters than even the 2017 Q series, and nicer cabinets. Although, the 6.5" driver in the 350 may add a little to the effects for the left and right for things like the battle scenes in Game of Thrones or background music that sets the tone in House of Cards. Tough decisions. Hell, maybe I just go with R100s/R200c for now and upgrade the 100s to the 300s when I can afford to...
Currently auditioning bookshelf mains
Currently auditioning HSU ULS-15 MK2 vs SVS PC-2000
NAD T757 with 758 audio card