Pioneer TS-G1040R or 41R (newer version)

It fits with relative ease, and improves the sound a bit. I went with the advice and added 200hz bass blockers/caps as well. A search will get you a couple of posts/results with pics.

 

And try eDead:
www.edesignaudio.com
for deadening products. A lot less $$ than Dynamat especially with the 20% off forum discount! $20 goes a long way there.

 

You can also hook up some tweets in the upper dash, you'll have to make a custom adapter(pretty easy) but the sound will def. improve while giving your speaker some room to breath. I also found that just buyin some cheap x-overs will help with the sound adjustment form stock to aftermarket. It's also a good idea if your replace the speaker wires from the amp(under passenger seat), I found that the speaker wire is much to small for anything other than stock apps. Good luck

 

Buy Good Dash speakers.

Many guys make the mistake of buying cheap dash speakers because they think
"it is small and does not matter"
"or it is small and they do not expect good sound to come out"
"or it is not worth of spending money on"

I am here to tell you that that is WRONG. The sound of your stereo is ONLY AS GOOD AS THE WORST SPEAKER. This is especially true for dash speakers. I have installed many speakers and it is scary how much you hear those dash speakers. If you place cheap speakers there you will hear cheap sound.

My buddy installed some speakers in his Honda Accord. He bought the same Pioneer REV speakers for Doors and Rear that I did, but he bought some cheap alpine 4in speakers for the dash. When he turns up the volume you hear the Tin sound coming out of the dash speakers.

Those JBL 452 4" speakers with external crossover are the best 4in speakers I have ever heard. Worth every penny.