Sorry in advance for a long-winded post. For my "secondary" system I have had a Yamaha 5740 with M22s and Velodyne CHT-8 in our living room and have been very happy. The receiver is rated for "POWER RATING 1kHz @ 8 OHMS = 6 X 100 WATTS, POWER RATING - 20Hz - 20kHz @ 8 OHMS = 6 X 85 WATTS" (copied and pasted from the Yamaha website). Due to geography/ease of use we wanted to use this receiver to drive speakers in our bedroom and on the outdoor deck by the pool as well. So, Friday we had someone (been in business 10 years, done work for several colleagues over that time with good results/knowledge, etc.) come hook up/wire the system through a 4 way switcher (would be happy if someone could tell me the correct name for this device) setting up 3 zones (living room, bedroom, pool - all speakers are 8 ohm, 2 speakers per zone plus sub in living room) and leaving one of the zones unassigned/speakerless. Since that time, the receiver has had the habit of just spontaneously cutting off if it is set anywhere near a high setting (it goes from -80 to + 15 and will cut off after a while at -15 which is not really that loud). I haven't had a chance to really check it out and see that it is all wired correctly (I'm typing this at work) but before I do I thought I might get some thoughts from the very helpful people here.
My thoughts/questions include:

We bought the wrong receiver for this purpose, but based on what was availble at the time that we were shopping with Best Buy gift certificates it seemed like a reasonably good receiver for a reasonably good price that would allow for possible expandability/backup for home theater and that 85 watts would be powerful enough to take care of any of our stereo needs. True?

Because my wife insists that the components (receiver and CD player) be put in the cabinet and the CD player is currently sitting on top of the receiver, it may just be overheating and I need to rearrange things to allow for adequate cooling?

Does having 6 speakers (although this problem happens with just one room turned on also) cause this type of trouble and if so is it because the resistance is too low - like trying to drive a 4 ohm speaker? Or am I totally confused?

If is not something simple like getting the CD player off the top of the receiver what is the best solution? HK 3480 stereo receiver? Separate amp? I'm open to suggestions.

I apologize for asking for help before I have really checked out some of the simple stuff, but it is on my mind and has raised some questions in areas that I would like to better understand anyway so I figured I would just go ahead and throw it out...

Thanks in advance.