Mapman..what is important to make the comparison is the gain output, the max amperage output and voltage storage.
Class D amps work best with dedicated 20 or 30 amp a.c.
outlets since they move current by means of pulse modulation or switching modualtion. Comparing the Simaudio 400M to the Bel Canto Ref1000M, The Sim has 100,000 microfarads of storage if you count all main and secondary caps and has a max output of 56 amperes where as the Bel Canto peaks at 45 amperes, the Sim has a superior power supply. I have owned Class D amps in the past. They are great if the recording is good quality but since Class D amps are known for being extremely neutral, they can be brutal on poor red book CD's. Class D amps do not have the full, liquid midrange of the best tube and S.S. amps. I had the Nuforce 9SE V2's, and they where too dry in the upper frequencies. A close friend of mine in Chicago has the Sim 400M's with a Levinson 326S Pre and a Playback Designs MPS-5 SACD player. He describes the Sim's as very organic with a very full rich and smooth midrange, with outstanding transparency and echo decay. Class D amps are good if you are on a budget and want a short cut to obtain high power, but they are cheaper too make and do not possess the superior beefy power supplies and larger transformers of conventional amps that will always have greater power reserves then Class D.