Loudness is a stupid concept but I know you just want your tunes louder. Well the first place to start is to listen to the mix. Is your snare loud and crisp or is it kind of there but not quite? High end makes most of the "loudness" you're talking about. Next thing to listen to is the overall balance of the drums. The high stuff(hats, perc etc) should be audible but still a bit lower than the bd and snare. The stuff that "hits you" should be more toward than stuff that's just basically chopping the beefy parts up. or you will have the "minidrums" effect. I hear it a lot on the forum's productions....
Make sure everything that shouldn't have bass or even sub-low frequencies, is high passed. You can be quite aggressive with the HP filter especially when it comes to wobbles or other mid range bass sounds. The sub is where most of your headroom goes, as far as a single instrument is concerned. Lower sub volume = more loudness. Although, less sub might also be too thin or just wrong sounding. You have to experiment. Try some heavy compression and limiting in the mixing phase of the drums. You can then "have it lower" signal wise but it'll be as loud as before limiting. Some tape saturation couldn't hurt either. All you need for the master now is 1-2 db of normal, slow compression and a limiter/clipper taking away MAX 2db.
hope this helps
