Well not sure how much this will help those of you who are looking for upgrading your stereos but i just finished replacing everything. First off was the head unit. I didn't want a cd player, just something that plays the radio and ipod or mp3. So went out and found a perfect unit for the bike. Below are pics that shows my old set up and the new set up. The best part is that you actually put the ipod inside the unit so you don't need to worry about mounting a holder for the ipod or mp3. The unit i bought was last yrs model which cost me 150.00. This yrs model for an extra 50.00 is fully water resistent. Looks exactly the same. I didn't worry so much about the water since i have a cover coming in for the stereo. As for the speakers, the sad part about 4" to 6" speakers is that they don't handle bass. They weren't designed for that. It's the bass that always destroys them. If you turn the bass down , the speakers will last longer. For the most part i find if you have an older head unit, your speakers won't make that much of a difference whether you buy a 20.00 speaker set or 100.00 speaker set. In the end everything is based on you stereo. What it puts out for wattage. The newer unit now generally put out about 45 to 55 watts per channel. At which point now you can look at getting more reliable speakers. I actually just spent 30.00 on JVC 4" speakers and to my surprise sound amazing. They are 25 watts RMS and 125 watts max. And also the newer head units these days produce more then enough wattage that installing an amp is not needed and speakers can handle a little more bass to them.
But this is just my opinion. I drive to work doing 75mph with a really short windsheild and the wind hitting me in the face and i can still hear my speakers. But once my new taller windsheild gets installed those speakers will sound clearer.