Hi, first, congrats on your decision to buy an ody, and welcome to the club!
Although I agree the stock system stinks, you really should listen to it and get a baseline first; the 2002 is a bit better than '99-'01 and you might be reasonably happy. If you decide to upgrade the minimum thing to do is upgrade the front speakers. They will make the most difference in sound quality.
You'll probably need to spend, at a minimum, around $40-$50 for an upgrade that will give you some noticable "improvement". Many people here buy Pioneer because they fit very well and easily in Hondas, and they represent a good value, esp. if you buy off the net.
Pioneer TSA-1665 and TSA-1695 are the two most popular. There are MANY MANY speaker choices out there and this is a subjective decision. I recommend you go out with a limited # of choices and audition. Keep a price limit and you can easily make a decision that suits you best.
I don't recommend upgraded tweeters myself, but many like them. Try the door speakers first and see. If you want more brightness, you surely can go tweeter route.
Read through some of the speaker upgrade threads in this forum; this discussion has ocurred time and time again. If you have a specific need, let me know and I'll try to help.
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-Shin John
'01 DEP EX, and I'm workin' on it! (slowly)