In the U.S. it appears that you'll only get about $500-$550 for it. In Europe, the same machine would snag bewteen €700 - €800 euro. Of course, the machine's did cost more to begin with. Unfortunately, the new eMacs have just put downward pressure on your selling price. Also, it really does seem that people don't place too much value on extras like the AP Card or RAM.
I'd pull the Airport Card and sell it separately to an iBook owner!