That's good advice from Cyb and Rev. Wish somebody told me that when i spent (wasted) big bucks on my stereo for my first car (A real bomb). It was a VH Holden (GM) Commodore 6cyl and suffered from bad road and wind noise, including major mechanical problems.
I put a Kenwood system in it, including a Kenwood 12' sub in a custom wooden parcial shelf which seemed like a good idea at the time to save boot space but when i cranked up the volume the whole car vibrated terribly. When i eventually sold my car 10 years later i only got $500 for it (original value: $6000, total cost:$10,000!) I updated to a newer Commodore, VR Exective (Holden fan!) took my 10 year old system out and paid some guy $400 to re-install it.
Bad move... The rear speakers were cracked from the sun and were totally fucked up. Wasn't long before they blew, followed by my front speakers, dashplayer and amp.
So i had to throw them all in the bin and buy a new system. I got a Sony Explode dash player, 4 Pioneer speakers, Pioneer amp, Clarion tweeters, and a custom made sub box with a 12' Clarion woofer which pumps nicely. I also got a 10' sub behind the seat which i don't use any more and still got one of the surving Kenwood amps from my old car which drives the Clarion sub. It's a mix mash of brands cos i couldn't afford it all in one hit.
I've had my car for four years now so my dashplayer is a little outdated
(as is my car!) It plays burnt disks but no MP3's but i do have a MP3 player connected to it so its not all bad. My dashplayer also has no sub volume output so i can't crank it all the way or else my speakers will distort but i don't care - its loud as it and i definately won't be spending any more money on it!