Sound system question

I want to wire in at least a new sub and possibly some better speakers into my 09 EX-L V6, but I wanted to keep the stock head unit if it’s possible. I’ve heard of people doing it on ninth gen civics and accords but I don’t know much about the eighth gens since I only got mine back in December. Was wondering if anyone else had tried to do what I’m doing and have any advice. I just want to try to keep the stock radio since I don’t like having huge screens and I like my cd player