1. RMS = Root Mean Square - generally, if talking about equipment that isn't utter crap, RMS will be your TRUE power rating - Peak is a load of bollocks.
2. In car audio (and PA), it is considered normal practice to use an amp that is rated for double the power of the speakers it's running. This is to account for Acoustic Impedance - the lower frequency something is, the lower the impedance, the lower the impedance, the harder the amp is working, etc.
That's why whenever you see that impedance on a speaker (4Ohm generally in car audio), it's 4 Ohms impedance at a frequency of 1kHz.
3. Yes, it can. Not saying it WILL, but it's definately possible, and it does happen. Standard procedure with audio equipment is that to prevent the "pop", the amplifier is ALWAYS the last thing to turn on, and the first thing to turn off.
Set up a 555 Timer (I think) like most people on here seem to, and allow a delay before the amp turns itself on.
Damn, here I thought I'd never spoonfeed again.
and are your friends.