selecting amp

Ok, I'm a little confused here, I have a friend who said that i need to get an amp that will not under power my speakers.  He said that it is easier to damage my speakers by underpowering them than by overpowering by burning out the voicecoil.  I do not understand why that is true or if it is. Could someone please explain?  Does this mean i have to get an amp that has more continuous power than what my speakers can handle and turn the gain down or does it mean that i can't get an amp that will grossly underpower (e.g. an amp that puts out 25W RMS to speakers that can handle 100W RMS)  my speakers?

About my system;  I have front components that can handle 140W RMS, rear 2-ways that can handle 80W RMS, I would like to get a sub like the JL 12W3v2 that can handle 300W RMS.  The amp i am looking at is the JL 500/5 that is 100W RMS x 2 at 4 ohms for the front, 25W RMS x 2 at 4 ohms for the rear, and 250W RMS x 1 at 1.5-4 ohms for the sub output.  would this amp work well with the speakers i have listed above?

You can underpower a speaker all day long, provided the gain on the amp is set correctly and you are full aware that a distorted speaker is something that you have caused. This means that either the gain on the amp is too high and sends a clipped (distorted) signal to the speaker for it to reproduce, or the signal coming out of the cd player is clipped from either the cd itself in the recording process or the level it is being played at. Keep the bass setting a nominal and do not use bass boost settings if it can be helped. Do you have a cd player yet and if so, what kind is it. Great choice on the amp.

Thank you guys that really helped out! 

BTW my friend wasn't saying this JL amp is bad, in fact he said it looked really good.  We were just discussing what could damage speakers and he mentioned that underpowering them could.  I just wanted to make sure that the 25W RMS on the rear channel won't damage the 80W RMS coaxs'.  I am also the type of person that always wants to know how and why something systematically works.  I appreciate all of your responses.

forbidden - i have an alpine cda-9827 for my HU.

I currently have an Infinity Reference 7854a amp that puts out 111W x 4 RMS, however i am getting a lot of noise(speaker hiss and alternator wine) and am trying to figure out where its coming from.  maybe you guys could help me with this one as well. ;-)  i know its not coming from my HU because i can have the RCA's and the remote turn on unplugged and the speakers still make that noise. (i jumped the remote lead on the amp to the power wire to turn on the amp)  i tested my ground with a multi meter and i have continuity and shows .015 ohms on the ground which i think would be acceptable.  also my ground cable is the same gauge as the power wire (4 AWG) and its only 3 1/2 feet long.  i plugged in a much smaller amp i think only 40X4 and i didn't get any noise.  i then borrowed a friends infinity amp (exact same model) and hooked it up to my system and got the noise again.  is it possible that this model amp is eather crap or that it won't work on my system for some reason?

one last thing i promise!   i am one who really appreciates good clean sound, not how loud my speakers are or how hard my bass hits.  will this sub be a good choice for SQ or is it known high SPL, or with a 12 in woofer does SQ play much of a role?

sorry about the long post, and thanks again!

thank you sedate for the info on the perfect kappas.  and yes i did purchase the amp from a mainstream place from a friend who worked there using his discount of course!  well i learned my lesson on trying to pinch the penny!

does anyone have expierience with the audiobahn subs?  i have heard some of their higher end stuff and it sounded great.  in fact my component fronts are audiobahn and i am very happy with them.  and why can i find a lot of audiobahn stuff for cheap on the internet.  for example the speakers i bought from carstereodiscounts.com and they were discounted because they where last years model and  a friend of mine bought some audiobahn stuff from there at a greatly reduced price.