I am currently running 2 MTX thunder 4500 (500RMS total) And whenever any bass hits, not even that loud my deck dims. My lights will dim, everything dims. I dont think a cap will help so I am looking at upgrading my alternator to a high output. Will this help? O its a 96 cavalier btw.

 

Start with the big 3 upgrade. Use the search button ^^ and there is lots of threads about this

 

And chances are that your battery is totalled as well.