I only have a standard cab and I put boston accoustic 6x9"s in 2 separate boxes behind the rear seat, and 2 alpine 6.5"s in the doors. Also I have a pioneer 50x4watt head unit. Does anyone think I should get an amp to let these speakers scream more? or does this sound plenty loud for my small enclosure, I was also thinking of maybe more 6x9's in the back, either custom mounted in the rear side panels, or just more boxes.

 

I would go with an amp.

Aint nothin like MORE POWER

 

Add a small sub and an amp and you will have something there. Seems like what you lack more than anything else is some real form of bass. I suggest a good quality 4 channel amp running in a 2 channels stereo to the front speakers only and 2 channels bridged mono on a subwoofer. It would be a good start anyway and later down the road you could get a seperate sub amp and double the power to your mid/high speakers with the extra 2 channels you will not be using to drive the subwoofer.