Ohms (no, i'm not meditating, though maybe that would help)

[Ghoulish Delight]

Amp and speaker impedance. Drives me bonkers. I get confused enough without the added obfuscation of marketing numbers vs. reality.

So I'll try to boil this down to a simple yes or no question.

For an amp with the following specs:

Power: 165X5 @3ohm
Power consumption: 165W

Can I swap out a 3ohm speaker for an 8ohm? Do I need to know anything more about the 8ohm speaker and/or the amp it's currently connected to before answering that question? If I use 8Ohm speakers on 2 of the channels, would I then be risking over-powering the 3ohm speakers on the other channels?

argh, this sh*t gives me a headache.