@PeteS - Hmm, interesting...it rather depends on what else is happening at the same time, what instruments are playing, and where they are in the soundstage. Take something like FabFilter pro Q3 or the free span and check out shat the frequencies are doing.
Sometimes you have to carve the bass frequencies from other instruments to make sonic way for the dark bass, some folk add a sub bass plugin like Bass Mint (which does a great job) but might not be the answer, as that will add the feel of a sub bass, not necessarily the sound of a bass gtr...when I get a problem like this sometimes it's down to the choice of bass cab sim...Had exactly the same issue in my latest release, where there such a lot going on.
Also ensure you have enough headroom in your mix (correct gainstaging), have about 10db to play with on all the other instrument fader meters, especially with bass, it'll EAT your headroom and that's all you'll hear bass and nothing else.
I'd also advise to listen on a bunch of sound sorces as each one will respond differently, headphones, phone, studio monitors, car...
Hope this helps Peter, and good luck with it.