Good morning!

I have a stock NP300 Navara which I'd like to upgrade a bit for better sound quality. Nothing too fancy and loud, just want good quality audio while driving etc.

I plan on upgrading my HU first then add an underseat amp and underseat sub. Might also upgrade the 4 stock full-range speakers to better mid-range speakers and then the 2 tweeters. For now I'll do the amp and sub first though.

Can anyone recommend a good quality budget amp and sub? Again, doesn't have to be too loud just as long as it will improve overall sound quality. Thanks a lot!