Of the 2) 2 channel amps listed I would go with the 402. I have one and love it. I had a 352 and really didn't expect much when i bought it I just wanted to get away from the changing of the bulbs. But the 402 is a newer design than the 252 and has a few differences that add to a better sounding amp. One is the newer design power supply, to which accedit the better sound over the 352 I had. And second is the "quad balanced" circuitry also referred to as "dual differntial" in earlier Mc amps. This lowers the noise floor of the amp.
Best Amp for McIntosh sys.- MC252, MC402, or MC501
I am upgrading a system that I have for about 40 yrs. Recently purchased a MCD301 sacd/cd player, MR85 tuner, and Paradigm Studio 100 series IV speakers. Still have C26 pre-amp and MC2505 amp (both recently serviced by MAC). I am happy with the sound but am afraid the days of shipping the amp back and forth for service are limited. The spks are rated "Suitable amp power range 15-350 watts" and "Amplifiers that exceed-power range are recommended". I don't intend to make another amp upgrade and am leaning toward the 501.