stereo upgrade....any ideas?

I have 1990 full size truck with upgrade pioneer cd player and ready to upgrade more. Any ideas out there? No extened cab but i am planning on a sub behind the seat. Probably should upgrade the 4- 4x6 speakers that came stock as well. Any ideas suggestions would be great. Let me know what worked for you. Not looking for stupid loud but good quality.

I would get all new 4x6's I would Pick Pioneer for good sound and price.....but if you really want it to sound perfect!!!! get Boston Acoustics!!....
The prices are about $120 for 3 or 4 way pioneers and about $300 for some good Boston's....
But you know if you get a Sub you need to get a amp and if you want your 4x6's to sound better you can also get a small amp for them as well