I had a Chord SPM600 (and a Chord pre) powering Raidho D3s. It had all the power I needed but it lacked an element of timing and separation/detail of individual percussion instruments were somewhat "blurred".
I have since upgraded to an Aavik U-300. This captured all the timing and separation of instruments was now very much clearer. The only downside was that it does not have the power of the Chord (the "slam" for want of a better word). I often find myself using the Aavik to the upper-end of the volume dial while the Chord was at only 60% or so. But the detail from Aavik is so much greater.
I auditioned the Nagra Classic mono blocks also. These certainly have the power and "slam" I like and provided an excellent soundstage with wonderful resolution and detail -- however, due to complaints by the neighbors (philistines) I am now compelled to play at moderate volume (until such time I move house). Thus the Aavik does the trick perfectly.
I also upgraded the cables from Nordost Valhalla to Ansuz D-TC and the noise floor simply disappeared and I hear so much more detail than ever before, certainly from vinyl playback.
Lastly, I have just bought a pair of Raidho D4.1s ... while they've not arrived yet I expect to get even more detail and finesse at normal volume.