You want the router placed as high as possible and the antenna also placed as high as possible. An extension cable will let you at least put it on the top of your desk where you can move its position around to find the best placement.
The difference between a Belkin vs Linksys USB wifi adapter (other than Belkin's proprietary N1 protocol which only works between Belkin products) is not going to be significant but antenna placement will make a fairly large difference.
Edited to add: If the signal is poor it is almost always due to the transmitter (router), not the receiver. Upgrading your antenna/router will yield much better results than messing with your USB adapter providing your USB adapter isn't a no-name cheapie.
Edited 1 time(s). Last edit at 10/22/2011 06:16AM by Death_Claw.