That is a very useful link, I never realized it existed. Well, I was indeed wrong, results:
Wired cable connection: 4.4mb/550kbps
Wireless-G connection from upstairs: 2.5mb/330kbps
However, I just figured out the deal with reception, ANTENNA PLACEMENT!!! My computer is near a back house window upstairs, while the router is near a window on the same wall downstairs. The router sits on top of the pc tower directly in front of the downstairs window. I had all three antennas directly verticle (best reception from my experience with Yagi elements), where I was getting the 36-48mbps. I simply aimed the 3 antennas at a 45 degree pointing out the window, and bam, now I have the 54mbps the Linksys was getting. So small movements with antennas can make substantial changes in connection quality.