Car speaker question....

I have a 2006 Chevy Colorado. I love it, it's been a great truck, very reliable. I'm still using the stock stereo with Sirius Radio, coupled with my smartphone and a FM Transmitter, I pretty much have it all.
The problem, my speakers suck.
I don't need it to be too loud, but I do like to crank a good time from time to time.

I am a complete dweeb when it comes to speakers, stereos etc. 0 knowledge.

Anyone have any advice on speakers, without going too overboard pricewise. I don't want to add an amp or sub woofer, just looking for something reasonable with good sound and reliability.


Here's the sizes

Front: 6-3/4"
Rear: 6-3/4"
Front door: 6-3/4"
Back door: 6-3/4"

thanks.