I have the privilege of owning a pair of Kensingtons. I have owned 12inch golds, my father owned 15 inch golds before buying the Kensingtons shortly before his death (he really knew his stuff and said the Kensingtons were an almost perfect compromise speaker). I have to say I cannot fault them and although expensive they trounce almost all the exotica I have heard at many times the price. Although not an easy load they are not an appalling load, or very inefficient, so are drivable by amps a non-millionaire can afford. I would however recommend SS not valves (long story). The great advantage over the larger Prestige drivers is cost and to be honest I don't want a speaker much bigger. Their bass is of outstanding quality, but it isn't "vibrating your stomach" intensity. I much prefer the bass to larger coned Golds, but haven't heard larger coned Prestiges. Listening to a live Radio3 broadcast through a NAT01 (fed by a Galaxy17), TEAD Vibe / Pulse2, Hovland Radia, I do wonder how much better anything could sound.
Nic P