I've smiled when i've saw the tittle of this thread, because when i've bought the Dyns X12 one of the speakers that i've wanted to demo were Totem Rainmaker and the KEF R300 and never did!
so, still have the Dyns x12 and have no wishes to change them in a near future.
I had the Brio R and X12 for a year and love the combo but as Dave have mentioned some times the lack of power of some amps can make some speakers sound boomy at low end, and that was exactly what i experimented with the Brio R.
Having upgrated the amp for the Pathos the extra 20wpc actually make all the difference, the controle over the bass at low volume is amazing.
Excite X12 are the easiest speakers to drive in Dynaudio range, they have a very linear response never getting under 4ohms, information provided in Dynaudio web site, but still adding some challange to most 40/50 even 60wpc amps.