I find that I always make the kick louder than I think it needs to be in the mix.... I always found it wasn't loud enough by the time I added all instruments. It's much easier to pull it down than boost it. I used to try to seperate different parts of the lower freq, say the kick between 50 and 80 hz, and the bass between 80 and 120hz.... then reallized that as long as I kept the bass guitar under the kick, it all works out, and they could both have their fullness with only minor eq... even if the kick drum is masking some bass guitar freqs, it's only for a split second, you're still gonna hear the bass guitar in between. However, if the bass guitar masks over the kick drum..... if you're lucky, you might here a little of the kick drums attack, if anything at all.
Keep in mind, though, I mix rock/metal... so my idea of good is a bombastic pound-your-chest mix.