Compression. Sounds like you need it. (on more than the drums).
For rock and metal kicks, I'd gate until the kicks are isolated. Compression with a hard knee, about 15-30ms attack, 25-40ms release, a 4:1 ratio, and adjust the threshold until you bring out a nice transient peak. Then, about a 3db low boost around 75hz, a 3db cut around 250hz with a wide Q, and boost around 5khz with a narrow q to get the kind of definition you want. Small boost for rock, more boost for metal, insane boost for death \m/, etc.
Whatever you do to the kick, do the opposite for the bass. If you add 3db at 75hz to the kick, cut the same from the bass. Though the fundamentals of a lot of your bass guitar will be below 200-ish hz, the counter-intuitive thing is that most of the meat is actually in the low mids. Just take care not to overload the low mid area because that's also where mud lives. Good luck.