Yes. You need to mod your OEM enclosures, have a template made, or purchase some from SOS or Angus (I think Angus sells them, but I may be wrong). You also need a wiring harness, which I purchased from SOS.
You can use any speakers you like, but I'd suggest 5-6.5 inches in size.
You will also need an amp to power the speakers.
I have the OEM headunit and use JL Audio XR speakers. I have 6.5 inch speakers in the doors and the tweeters mounted by the mirrors. Do a search, there's tons of information out there. In fact in my thread a few years back, Malibu Rapper basically walked me through how to install my own system. :biggrin: