your in the same boat as me...i have 2 computers hooked up to a wireless d-link router and let me tell you...
1. cordless phones will interfere with the internet signal
2. try using the microwave and see what happens to your d/l or u/l rates ( they go to zero )
3. if you have any other wireless products in the house..such as headphones, speakers , ect ect ect then your screwed
take it from me ...its a constant battle...I really can't do anything about it as i live in the basement and i share the internet connection with the people upstairs.