So my rear speakers sound terrible! Not sure if they were blown prior to me buying it or if Buick just put crap speakers in, hardly any bass. Any way, does anyone know what size the back deck speakers are? If so, has anyone replaced theirs yet to aftermarket? Were the results worth it? Is there an amp? If so, where?

 

One of the best places to obtain replacement vehicle speakers for me has been "Crutchfield". They have extensive fit/application charts- data, and all kinds of adapter harnesses, brackets, etc. A good place to deal with in my experience. https://www.crutchfield.com/S-PcEG2r5T65J/