Take a leaf out of dubstep, you want to feel things like this more than hear them IMO, I prefer them to sit that bit lower in the mix just so you can kind of feel your subs having a bit of a freak out when they hit. A good idea is having your mix bus high-passed to around 25 - 35Hz, not high enough to notice, but enough to not make your master limiter crap out when your want a sub drop.