mach 460 replacement help

Just wondering how you added the sub to the mach 460? Do you know what wires you tapped into for the line level converter?

Definitely ditch the stock head unit and front speakers. For the HU, I'd get an Alpine CDA-9811/9813 depending on your budget, and for the fronts, get some Alpine Type-R 5x7 coaxils/5 1/4" components. You'll have to run new speaker wire from the HU to the speakers, or at the very least tap into the wire right before it goes through the door. There's not really any drop-in speakers you can add to the Mach system, because the mids and tweeters are run by seperate amps and crossed over at frequencies not really compatible with other component speakers. For the rears, I'd just leave them stock, disconnect them, or get some speakers for rear fill: http://www.thezeb.com/caraudio/CDT_Audio_FullRange.html.

If you wanted to go even further, I'd get a nice 2 channel amp(100+ x2 RMS) for some CDT CL-61 or HD components http://www.thezeb.com/caraudio/CDT_Audio_Components.html for the frontstage, the CDT's I mentioned above run off the HU, and remove the soundboard from the back. This, with the HU, might be over your budget, but will give you a better overall sound than the setup above.