mc402 vs 501 monos vs mc 602 with B&W802d

The MC501s do sound better. It's not a huge difference but if you ever owned one, you would clearly hear the difference. It's unlikely that you would need more power than what you could get from the MC402. I have owned both amps. Knowing what I know now, I would have bought the MC501s in the first place. If it's at all within your budget, get the MC501s. IF however you never hear the MC501s at home, you likely would never have a reason to not like the MC402.It is hard to tell how much of an "amateur" you are so I'm not sure how easy it would be for you to tell the difference. However, I believe most guys in the hobby would be able to tell.

Beg to differ saying the MAC MC402 barely has enough power at 400W to drive a pair of B&W 802D speakers.

I own a pair of the big brother speakers of B&W 802D's the 800D's. The McIntosh MC-402 amp easily drives a pair of B&W 800D speakers at more than anyone will ever need in loudness. Just make sure you have a great power cable on the MAC MC402 to get full benefit.

The 402 just barely makes it for the 802d if you like your sound loud. In auditioning the 402 with the 802d the power guard came on a couple of times on orchestral pieces. Of course this was a the limit of what the 802d would put out - about 110 spl at about 6 ft on the peaks. Still - for this reason I would recommend going to the 501 monoblocks.