Guido - Both have power supply built-in and connect to mains. 200ASC has switcher while 250ASP has traditional power supply. The strange thing is that there is no large transformer on the module - only something that looks like big choke on EI type square core. I checked block diagram and it shows that they rectify and filter mains and feed it to DC/DC converter. DC/DC converter is a switcher so no matter how you slice it both use switchers. Judging by size 250ASP is a little more robust and it shows in ability to drive lower impedance than 200ASC.
I had opportunity to buy cheap REF1000 from the dealer who was loosing Bel Canto line but was afraid of 1000W with my modest size speakers. On the other hand I don't listen very loud. 200ASC is described as sweeter but 1000ASP is praised to be a little more coherent and focused. The difference is very very small and the main thing is raw power that they deliver. Stronger Mosfets are always slower therefore switching frequency has to be adjusted to avoid losses and bandwidth has to follow. 1000ASP has -3dB bandwidth of 38kHz (8 Ohm load) while 200ASC is rated 60kHz (same load).
I had opportunity to buy cheap REF1000 from the dealer who was loosing Bel Canto line but was afraid of 1000W with my modest size speakers. On the other hand I don't listen very loud. 200ASC is described as sweeter but 1000ASP is praised to be a little more coherent and focused. The difference is very very small and the main thing is raw power that they deliver. Stronger Mosfets are always slower therefore switching frequency has to be adjusted to avoid losses and bandwidth has to follow. 1000ASP has -3dB bandwidth of 38kHz (8 Ohm load) while 200ASC is rated 60kHz (same load).