i would buy new speakers.... i have 2 blown stock ones in my car they rattle under any base... so i am going to replace them. and then pump it all with a new head unit, what are the names of a few headunits that are straight up bolt ins with stock brackets?
Actually most of the new CD players shall fit without any issues,but all comes down to make sure they are ok to going in the deck with no struggles.
Since you going to replace them think about a 3-way speakers all around