Upgrade My System

I want to upgrade my system and not sure what direction to go. I don't need to have subs just want a more crisp sound.

What I have- alpine headunit with 4 3 way pioneer speakers.
1 i was thinking of putting in 2 6 by 9's in the truck area to get a little more bass and i would connect the speakers by my head and the 6x9 to an amp.

2 should i just get an amp for the 4 speakers i have already.

3 will tweeters help me

And I open to any advice you have

Get a pair of good components in front + everything to make 'em work (2 ch amp, wires,...) That will make a ton of improvement.

Oh yes, a good set of components will make all the difference in the world for your sound. You usually get a little bit better bass as well as much more defined treble. You may have to spend 200 + bucks on a set, but it's well worth it.

jbl gti's are amazing. i have 2 sets in mine and 2 jl 12w6v2's, and they are not overpowered by the bass