2000 Accord Sound...

Just got a 2000 Accord LX and I was wondering if I should switch my sound system out of my old car or not and what the capabilities are of my new system in the Accord. I didn't do anything fancy to my old car, just bought some Pioneer speakers and Head unit and a 200 watt amp. No subs or anything, just hooked the amp into the normal speakers which actually sounded pretty nice. The problem is that I don't think the old speakers will fit into the Accord speakers places. Would there be any benefit for me to hook the 200 watt amp I have into the Accord's sound system or should I wait to get better speakers? Also, how good is the Accord's head unit compared to a Pioneer (its not a really fancy one)?

Any help/suggestions appreciated...