I've got a pioneer CD player in mine now (replaced the tape deck that the previous owner had in there to replace the original stereo), my EQ wouldnt let go of its screws, so they ended up getting broken off inside the EQ, so I had to pitch it. The only dash kit I bought, which was for my car according to the packaging, didnt have the pieces I needed to fill the space under the CD player so I've had a gaping hole in my dash under the CD player almost as long as I've had the car. Kind of used to it now, wonder what it looks like with a dash kit...
I've got 5" (6"?) 3-way speakers for the front doors (the tweeter part sticks out just a little too much, and bulges the panel) and some 4" (?) pioneers to go in the stock rear speaker mounts, but I would recommend taking out the stock mounts and making the back deck fit for some larger 6.5" 3-ways in the back, because the tweeters back there (there were stock tweeters in my car anyway, which I removed and put new ones in and subsequently took out) made too much noise for me. The treble in my car, even when turned all the way down, was too much for me to stand. Too tin-y or something.. high pitched.. If I had the money, I'd probably check out if my speakers are still ok (at least one is probably a bit fragged) and replace them/get an amp so that it sounds a little better.
In going from the tape deck it had in it to the CD player, there was a noticeable difference in sound quality due to higher wattage supplied by the CD player. So, whatever you get, make sure you can power it.
Greg