Wireless signal strength and noise levels

I've been messing with moving my wireless AP around. I came across this website (Boost Your Signal ) talking about wireless, signals, and antennas.

Last night I was using the Dell Wireless WLAN Card Utility and notice the signal from my AP is weaker than a neighbors. Tonight I moved the AP upstairs and more central in the house. The signal is stronger (stronger than the neighbor's) but I am noticing something I've not noticed before. The 'speed' reported by Vista is low, and when I am downloading it goes incredibly low. To 1Mbps. I've got a N card in the laptop I am using and the router support N. So why so low. I also notice while downloading the reported noise level greatly increases. Right now the signal is around -54dBm and the noise is -88dBm. I started a file download and the signal stays about the same, but the noise goes to -75dBm. The 'speed' went from 39Mbps to 1 or 2Mbps.