There is no true "gain" on this amp. There is a bass level, I would assume that is the gain. There is also a subsonic filter, input sensitivity and x-over frequency knobs, none of which solved either problem when I played with them. I dunno about the RCAs, they are phoenix gold so I would assume they are decent at least.

Maybe I will try moving the ground to a different location. Right now I have it under the mounting bracket to the backseat, I thought that would be a decent place but maybe I am wrong...