One thing bothered me about the install in my daughter's '98 Accord Coupe EX V6 was the fact that the car has tweeters in the dash. I replaced the door speakers with Kenwood coax speakers I had from a previous install... I used the factory wiring, so the dash tweeters and the Kenwood coaxes are both being powered by the mid/high amp. Thus the highs tend to be a little harsh. Also, I'm thinking that the resulting resistance of the Kenwoods and the factory tweeters seems to be reducing the output of the front speakers. The mid/high 4-channel amp also powers some Kenwood 6x9's in the back shelf. To compensate for the stronger rear sound I tend to want to fade toward the front, but that's when the harshness of the front gets to be a little tiresome at times.
For bass, I have an old JL Audio enclosure that seems to give the system a pretty full low end, but it isn't very punchy. I've offered to swap out the JL vented enclosure with one 10-inch woofer for a sealed JL enclosure with two 10's... but she hasn't shown any interest in making the change or even just giving it a listen.
Another thing you'll have to consider is are you willing to give up the steering wheel controls? Going with an aftermarket headunit will require you to buy a device from PAC that changes the signal from the steering wheel controls in to an infared signal to control the new deck if you get one that is remote capable. The original deck we installed in her car was a Kenwood KDC-MP522... it worked with the PAC box, but then promptly died. I happened to have an older Kenwood KDC- MP8017 deck laying around so we went ahead and installed it in place of her dead deck. I had owned the KDC-MP8017 deck for a few years, so it was no real surprise when it died a few months later. I just replaced the second dead Kenwood with a used Alpine CDA-7995... which I may replace with a CDA-7897 with the Fantom Face.
If price were no option, I'd love to power her system with a JL Audio 500/5 instead of the two Kenwood amps we're running.
Overall, the 6th gen (?) Accord Coupe is not a bad vehicle for stereo install. The panels in the dash surrounding the stereo remove pretty easily. Running a good sized cable from the battery to the trunk is a bit more work. Replacing the rear deck speakers is not as easy as one would think, the grills have to be removed... and if I remember correctly, 4 screws from the underside of each speaker aren't the only thing holding the grills in place. Once the grills are removed, you them have to remove screws from the top... the rear window tends to get in the way.
Also, swapping out the door speakers requires removing the door panel, nto just the grill. I never attempted getting to the dash tweeters... way too much work.
Ooh, almost forgot... if you're pulling the stock (double DIN) radio out and replacing it with an aftermarket (single DIN) unit, you'll need something to cover the space below the new radio. I haven't looked at any install kits for this, I just bought a pocket with a door to go below the radio. It all bolted into the brackets behind the dash... no need to use the DIN chassis mounting sleeve.
Sorry for such a long post...
JD