Cameron, Alan's description of the advice you read before as "misguided" is certainly accurate from my study and personal experience. You don't have to be concerned about being too close to the wall behind as long as the port has at least a few inches of "breathing room". One factor that is significant is that you shouldn't have the distance from the center of the woofer cones to the back and side walls equal. If they're equal, the room boundary reinforcement from the walls would pile up near one frequency, causing boominess, so keep those distances different.
