Did you try the R3s with a sub? Thinking it would temper the fatiguing highs.
Also did you try EQ? That might help as well, maybe even more.
Toe-out is the classic remedy for brightness. Containing surplus bass via placement, EQ, room treatment, etc is quite a bit harder.
Bass is an "assymetrical" issue. KEF engineer Oclee-Brown explains that they must cater for two different profiles: European listening spaces are smaller than (most) US ones. And European homes tend to have unyielding walls of brick and mortar while US homes make intensive use of wood and plasterboard that absorb bass (as a membrane bass trap would). This would help explain the European preference for smaller, precise, less bass heavy speakers such as the LS-50 meta and the great demand for Lintons in the US.
I lean towards the R3, but that's just me, in my location and listening room type.