The CYP AU-A300 is the polar opposite of what pure stereo amps are all about; a Swiss Army knife compared to a surgical scalpel.
Whereas something like a Yamaha AS500 or Marantz PM6004 are designed to keep the audio paths as simple as possible for maximum musical fidelity the CYP is designed as a hub amp/decoder for a large variety of entertainment sources.
Also, it's small, and that means it uses a switch mode power supply to create the watts. If you were driving some inceiling speakers or some <£100 bookshelfs then that might not matter so much. Or if it were a pure stereo amp then you might just get away with it. But with so much budget diverted to connectivity and decoding features required for HDMI, optical, coax, IP and RS232 control there's not much left for audio performance.
If it were me choosing a partner amp for the big relaxed Kefs then I'd look for something fast sounding and capable of delivering decent dollops of driver-controlling current as opposed to paper watts. The Yamaha above would be worth an audition. I'd steer away from the Marantz; too relaxed. But I think I'd be tempted to look at second-hand amps to really give the ex-£500 Kefs a proper matching partner.
Rega would be my first choice. Extremely musical and with enough pace to make the Kefs sing. An alternative would be Cyrus. These are small powerful amps based on conventional toroidal transformer technology so they have superb grip on the speaker drivers. Incidentally, I'm sure there's a Cyrus amp for sale in the Members Market. Could be a perfect match.
