Welp, since my computer is still giving me headaches in the wireless department, even with a brand-new connection, brand-new router, brand-new modem, and a roommate of mine having excellent signal reception not even ten feet away from me (but an equal distance away from the router), I have come to the conclusion that my computer's built-in wireless receiver is simply a piece of ****. Especially frustrating since this came as part of a high-end gaming rig I had custom-built, advertised as extremely speedy with wireless N capability (which it has never used and I can't figure out how to turn on... it's been stuck on G ever since I got it).
I'll go looking for a good wireless antenna, I guess. When I get a good one I'll remove the current one from the computer and smash it repeatedly with a sledgehammer. That may seem extreme but after literally years of randomly dropped signals, wildly fluctuating throughput, and general frustration, I think it's getting off easy.