More information, please. What processor are you using and how are you adding 10dB of gain? I am not familiar with the term "lfe db rating".
As a general rule, you only need to do the 10dB boost to the SW input when using multichannel analog connections. With multichannel digital, the software handles it on its own. With stereo sources, both analog and digital, no such adjustment is needed as there is no LFE to boost.