I can't tell if it is a mic issue or something else. I reversed the mics (left mic on right side, right mic on left side) and it produced the same problem. The left channel was still off.
The tricky part is I can't figure out easily how much to bump up each side. I'd like to get it as close to matched as possible.
If I'm reading you correctly, are you able to actually change which channel a mic goes into (i.e., you plugged what used to be the "right" mic into the left channel of the batt box, and the "left" mic into the right channel of the batt box)? I know the Coresound HEBs can't do that since they terminate in a single mini XLR, but yours may be different.
If you swapped the mics themselves and the left channel was off by a ton, that sounds like something wrong with the box. Do you have another box you can try? Or, have you tried running the mics without the box into something else (such as directly into the iRiver, or into your computer) and testing them at home?
Also, maybe Cool Edit is different, but I would generally avoid the "Normalize" feature. To simply just raise the volume of a channel (since most people record to peak out significantly under 0dB, and then raise in post to just under 0dB), it's best to use "Amplify" or the equivalent, which literally just amplifies the volume of the waveform, rather than "Normalize" which as I understand it amplifies different frequencies differently and produces more of a compressed, FM radio type of sound...