i used to have a PS3, many of you will remember back about 2 years ago i was heavy with the PS3, the best performance increase for the PSN is to DMZ it, and not even worry about the Port Forwarding, but if you have multiple PS3's then you'll have to set up some other form of networking, i only had one, DMZ'd it, and i would get around 30Mbps down on the PS3, being as the PS3 only has 802.11G you might wanna turn off your 5Ghz connection frequency and set your router to G only, this should increase your speed.
Furthermore, i have noticed a significant decrease in connection speeds with 5Ghz on this router almost as if the 5Ghz is greatly affected by range and obstacles. i never tinkered with 5Ghz before the 1.2x patches, but, i do know that the radio signal strength was unintentionally affected by this FW, almost as if someone sneezed while writing the FW and lowered the default maximum strength.
Also, set your SSID to invisible, and enable MAC address filtering, and then disable all WIRELESS PROTECTION, the invisible SSID will help deter people from connecting to your SSID and the MAC address filter will prevent anyone from gaining access to your internet, this will provide a faster wifi for the PS3 without an encryption key handshake interval every some-odd seconds, the wifi encryption slows the wireless connection speeds, WEP is the fastest security for G, but doesn't work for N that well... or at all.
WPA/WPA2 are the highest encryptions i can think of, and directly related is their decrease in wifi speed. N300 would be decreased to N240 or so, i don't use any encryptions, i just use the MAC filter and invisible SSID... recently though i think i disabled the invisible SSID, but i need not worry, the DGL-4500 won't get locked up or anything by X amount of ppls trying to connect, since i have a separate router handling my wifi as an AP to the DGL-4500.
try...
802.11G
2.4Ghz
MAC Address Filtering (Turn MAC Filtering ON and ALLOW computers listed to access the network)
be sure that the first computer you add to the list is YOUR current computer, so you can continue working on your router without having to reset your router back to default from a novice mistake by adding the wrong computer to the ALLOW list.
disable Wireless Protection, as it would be really redundant after MAC Filtering has been enabled.
Set the Wireless like this...
DMZ your PS3...
Enable MAC Filtering and allow only your known computers...