What you have to do i to configure well the router. I get now 270 mbps which is not 300 mbps but at least it went up a lot. Here is a copy of my settings:
Mode: Mixed Network Name (SSID): Default Radio Band: Wide - 40MHz Channel Wide Channel: 6 Standard Channel: 8 Security: WPA2-Personal SSID Broadcast: Enabled
That is what I have for the Wireless settings... Maybe sometimes the wide channel and the standard channel can vary a bit in wirless network speed because of the environment, like wireless telephones, or microwaves and walls that can interfere with that wave... Solyou just have to play a bit with the channel settings to see what is the maximum you can get by channel...
I have a Linksys WRT160N and my settings are essentially the same as dmxtec, but using channel 9 & 7 with WPA2 TKIP or AES encryption. The key is setting the T61 4965agn to WPA2 with AES-CCMP to connect at 130 Mbps. Otherwise you'll be stuck at 54 Mbps.