DI and a double with severe and and low cut and filthy distortion added and stereo widened to blend with the guitars.
I tend to fit the main bass in from about 60 to 120, just above the bottom of the kick, and blended with the 1st overtone of the lowest pitch of the gutiars (b, for me, normally, so about 120Hz). 1-ish through 2-ish k for pick attack and some cut from 150-200ish to about 700 to let the guitars low mids and mid come through.
I also more or less smash the $% out of both of them (6:1 or more, usually round 20ms attack, realease to track tempo), and I'm much more willing to record a bass in tiny pieces and assemble a bassline; its consistency and timing, even if its really low, is part of the backbone and glue of the track.
I'm looking to ways to improve this situation with impulses and LF exciters. I'll be experimenting in a track I'm currently recording. I say currently, I started ages ago, stopped, redid the studio, played with some mixes for people, and now I'm going back to it.
These are, however, just guidelines and starting points. You need to listen, and make reasonably intelligent changes to close the gap between how it sounds and how you want it to sound.