the bass in "modern" is pretty tight/focused. a lot depends what you're using as your monitors. I have a really expensive pair of AT headphones that unfortunately aren't that great for chunky guitar; I think they were made with lots of headroom for big farty hip-hop bass.
do you have the rec pre manual? if so, read it, it's really helpful.
If not, one of the big things to remember is that the Treble control, in all channels, is the "strongest" tone control (most amps are like this.) If you have the Treble cranked ('cause you're trying to do a "scoop") you are basically choking other frequencies out of the mix.
Because you have the same tone controls for, like, three amps, they don't have the same ranges across all modes. The modern mode is fairly pre-scooped.
To get a good aggressive tone in Modern I suggest starting with your gain and all your tone knobs at noon and your presence and master around 1:00, then begin fiddling *gently* with the tone knobs. Try cutting instead of adding-- if you want more of that scoop sound, roll out a bit of mid instead of adding treble and bass, if you want more bass, roll off treble. Taking the gain past about 2:00 will start costing you definition.
Also remember that that big huge big-bottom sound you get tweaking by yourself may just sound like mud when you have a bass player and a double-kick basement ape going too.
don't get discouraged, the rec pre isn't very plug-and-play, it's designed for organized tweaking.
