The problem you're having is that your PS3 and PC's are on two different subnets. I don't suspect you could get it working in the current configuration, you would have to add a static route between the 2wire and the Dlink pointing multicast in each device's related subnet to the other device. Since you have the cat5 from the 2wire RG likely going into the WAN/Internet port on your dlink, I don't suspect you could do this properly, and this likely wouldn't carry UDP packets between the two properly.
My recommendations are to choose one of the following:
1) If you're bent on using your dlink router, you need to connect your PS3 to it. I think all PS3's come with 802.11g WiFi so if your router supports it, that's one method - likely not the "best" solution for gaming, as there may be some added latency, but if the wireless signal is good - excellent, you likely won't notice much difference. The other option is a very long Cat5. run between the two.
2) Don't use your Dlink as a router and convert the settings so it acts as a layer 2 switch. This will place all your computers onto the 2wire's subnet so they can all communicate/"see" each other. The current method you have right now, really does not increase your security as the 2wire has an advanced firewall in it, on top of basic NAT. Having the dlink behind it sets you up for potential problems using certain applications. You would lose however the other features that you mentioned (D-Link's filtering, software firewall, antivirus).