What is the best way to add a 5:1 system

RR, your speaker switch should work fine. The only concern I would have is what it does to the sound quality of your MC202.

. . . what Jeff said. This is how I did it and it works great. It's also key that you choose a center channel speaker and amp matched to your mains. Likewise (but less so) for your surround speakers/amps.

db . . . it will work fine. I have a PAV that I use for Stereo (amazing stereo pre) and I moved it to my HT, using my Lexicon MC-1 for 5.1 input to the PAV. It worked fine, but because of ventilation issues in my HT rack it over heated so I had to move it to another system.

Thanx much for the tips. It will be a while before this happens, but thought I would get a vision for it should look like. Sounds like I will need a processor and another amp with 3 channels, or would it be easier to have one amp for the 5:1 and the 402 strictly stereo? That is how most of my time is spent.

I would go with your best/most favored amp for stereo and add another 3 channels of amplification for the surround. depending on your configuration you can get a 3 channel amp for the ctr/rears, or if you're like me and like to use short speaker cables, get a mono amp for the center (somewhat matched to your 402), and a pair of mono's or a stereo amp for the rears. If you get a 3 channel amp you'll need long speaker cable runs to your rear channels. Of course alternately you need long interconnect run.

The problem with getting a 5 channel amp for 5.1 is you need to swap cables, which is a big pain.