just to add to Rounik's comments. It would be good to know what other sounds the rumbles are competing with in the mix. Could you let us know what they have to cut through?
Sometimes these things are a bit of an illusion when it comes to perceived loudness. Compression is good to get the overall average loudness up but overdone, it can makes things sound smaller or further away.
Use the channel EQ, find the loudest lowest note and boost there... for weight and low end rumble you want to be playing in the lower 100Hz region.
However, as Rounik said, if you boost at higher frequencies over 2kHz, then you will bring out harmonics of the lowest rumble/ note and that will help give a low end illusion on speakers that can't play back the low notes.
Definitely Pan centrally so the booms and rumbles come out of both speakers equally... unless you want stylised effects like thunder claps coming from off center.
And, probably more importantly. Cut frequencies that don't help! Low mids/ mid range say from 150 to 1.5 kHz can be scooped out to draw more attention to the areas you have boosted. That range is also known as the nasal range therefore can make things sound weaker.
Hope that helps.