What's Wrong With my Internet??? :(((((

I have a home built desktop and I am having a little trouble with my internet settings. Here are my specs:

Intel Core 2 Duo E8400 Proc
Gigabyte DS3L P35 LGA775 Mobo
Sapphire Radeon HD4850 Video Card
Hitachi Deskstar 7K1000 1TB Hard Drive
Samsung 22x DVDR Burner
Antec 300 Case
ENCORE 802.11n Wireless Adapter
Belkin N Router

I've been playing DotA and noticing consistent spikes in my games. War3 is not a graphics intensive card so to check that its not my computer I played some single player and had no problems. My internet speed is usually 270Mb/s. The encore software tells me that I have excellent signal quality and signal strength. My noise strength is around 25%. My advanced settings are as follows:

Enable TX burst
Enable TCP window size
Fast roaming at -70 dBm
Cisco Compatible Extensions Disabled
WMM enabled
Power save disabled
Direct link disabled

Can I tweak my settings to improve my internet speeds? Or could there be any other issues causing my spikes. My housemate downstairs(where the router is located) has no spikes when we are playing DotA even though he is playing with a G wireless adapter. Could the fact that I'm upstairs cause these performance issues(when the router is downstairs?) Any thoughts or suggestions are welcome. Thanks in advance!