Use your old RAM with your new RAM, that way you can get 1.5 gigabytes of RAM, and that my friend, is A LOT. And since because all of them are PC3200 you won't have the latency lowered.
But what you can expect from that set up is a fairly good gaming PC. The CPU is really good, your 1.5 gigabytes of RAM will definetly be good(!) and your motherboard is really nice as well.
You should expect nothing more then a really nice gaming rig that holds the ability to upgrade in the near future. Overall, nice set up.