vibe subs - please help

what do u mean by a clipped signal

and what does an amp do when it clips

Clipping is when an amplifier is overdriven (usually by too high an input signal - most often caused in car audio by setting input gain or bass boost too high) and it "clips" off the tops of the signal sine wave.  This sends a momentary DC voltage to the speaker, which causes it to stop moving and produce more heat than it can dissipate.  This can cause it to fail.  Small amounts of clipping are normal and present in almost all systems.  Large amounts of clipping will destroy speakers (and can cause damage to amplifiers as well.)

Here's a nice description.

Anything up to 350 watts RMS may be used.  To be safe, do not exceed the RMS rating of the speaker.

It all depends on how much you want from the system.  I run a 12" sub rated for up to 500 watts RMS in my everyday car and run a 100 watt mono amplifier.  It's perfect for my everyday taste.  Use any amp and set it up properly and you will be fine.