Regarding "high frequency energy" with teh KEFs, be sure to check out the measured dispersion patterns of each model. Erin’s Audio Corner on youtube provides that info for several models and I have found that very useful to help understand the design and get things set up well.
ALso worth noting that at least with ls50s, kef provides very specific setup directions that takes the speaker’s dispersion into account, so be sure to follow the directions for best results.

