Raoul - Here's another thought. A while back I stumbled
on this website which has the separate stems for hundreds of songs. Its mainly for doing remixes, but I found it useful to download songs I was familiar with to just analyze and hear the separate tracks. It might be useful for you do the same and just listen to the stems of songs you like that have the low end you want and get a better idea of what's going on in the mix.
Might help.