To me not only is the sound system a good upgrade, but the VX is waaaaay bad for speaker boxes. After upgrading my brothers 1991 celica way back in the day, I had a chance to see a real manufacturer speaker box desing. This thing had hard plastic and molded "live sound" boxes with wadding, etc. and port openings- 4" front and 6.5" rear. I ripped them out of the car when we had to part with it (died a horrible SCCA rally death with almost 300,000 miles. lol) I am attempting to turn, twist, etc them to see if I can find a way to install them in my truck.

The point is- before you even go shopping for speakers, I would research how to either dynamat, sound box, etc. the new speakers that will be installed. In the back, there is absolutely nothing for sound. Just a metal bracket to hold the speaker which is basically a freestanding, suspended, open-air speaker setup. Even if you did a sound setup before aftermarket install, you would have better sound, and would only have to trim slightly for a deeper, slightly larger diameter aftermarket speaker. I personally hack- sawed the rear metal bracket in two pieces vs. one so I could have 4 6.5". In the front, the tweeters are fine, but the thin plastic/thin metal door with no box leaves much to be desired as far as a place to mount the bottom speaker.

Oh yeah, good luck if you decide to do the rear. My advice- whatever you do, do it all at once, and schedule plenty of time for the job.