If there are no clip lights on lc2 or amp you still have room to raise
Secondly you might want to run some test tones like 80hz, 70hz, 60, 50, 40, 30, 20 etc and see if the bass in the sub rolls off to see if you are even getting proper signal
Or even a 100hz - 20hz sweep
If for example 40, 30, 20 hz is significantly lower or non existent
Then there is a signal issue
Secondly you might want to run some test tones like 80hz, 70hz, 60, 50, 40, 30, 20 etc and see if the bass in the sub rolls off to see if you are even getting proper signal
Or even a 100hz - 20hz sweep
If for example 40, 30, 20 hz is significantly lower or non existent
Then there is a signal issue