Thanks for the suggestion Micca. I tried line-jack and this is what I got:
Sound still only comes out of the one right channel, but if I leave a cable plugged in half-way into the jack, I can hear out of both drivers. If I do a stereo test to see if the setup is working on my computer, it will play both channels, but now it shows that it's playing the right channel from both sides with no sound from the left. Basically, it sounds like it's in mono. Does that make sense? Also, I don't know if this has to do with what I tried, but I can hear background static from the amp now.
So far, I haven't been able to tell what exactly the DAC changes in the music. This is from playing FLAC through my K601's, so I don't think there's anything that would hinder me from hearing a difference. Of course, I'm not going to make a definitive opinion considering my situation.
If no other suggestions, L7?
Hmm, short of sending them both in, the L7 kine out kit seems to be your best solution.