Are you having any problem with intermittent switching behavior with the C60? I have the Yamaha C-70, which looks the same as yours, and it has internal connection intermittency.
I had a friend who had a Kenwood M2 driving a pair of AR 9's. It was a fantastic combination. He used a C1 as his preamp. I really liked the blue meters. It was a perfect match for his Aiwa ADF-770 cassette deck.
I was so impressed I ended up buying an M2a and a C2 as the basis of my 1st real system. I had already bought the same Aiwa deck, but by that time, the M2 had been replaced. The meters were replaced also.