Rok, I had a problem with my right channel being louder than the left channel. Since I'm an electronics technician who put this rig together with attention to detail; how could that be possible?
That problem nearly drove me crazy, no matter what I did, the problem remained. It wasn't until I had a hearing test that the source of the problem was revealed. Ages ago, in the Air Force, my left ear drum was injured in a rapid decompression incident, and as many injuries, they get worse with old age.
The only solution is headphones, and I hate headphones (can't wear them for long). Now that I know what the problem is, I simply live with the louder right channel.
No, turning up the other channel only makes it worse, because you will hear that sound bouncing off the opposite wall.