You don't necessarily need an amp sim to get a good recording tone with bass. If you have a decent enough bass with onboard tones set how you want (i.e. fiddling with the tone knobs), try recording the DI (as you've done) on one track and copy and paste it.
On your first track, set a LP around 3500 to cut the highs and do a big dip a few db around 500Hz with a Q between 1.25-3.5 (to taste of course, use your ears) then compress the ever living shit out of it ... this track is going to be your bottom end of the bass.
On the second track, set a HP all the way up to around 550-600Hz (12db slope should do the trick) and LP everything from 4000-4500kHz (to taste of course) since everything above that is pretty much nonsense for bass ... you can get lower if you want to give your guitars/drums/vocals more room, but that's entirely up to you. Now add some distortion ... I recommend
"NoAmp!" which is based off a Sansamp bass driver ... not the best emulation of it, but it's perfect for what I need it for, sounds good, and it's free. It's a windows-based vst, which I know you're looking for a Mac-based plugin of sorts, but all the plug-in consists of is a .dll file (I dunno if you can execute those on a Mac since I'm a PC guy, so don't burn me if you can't!). When you add whatever distortion you decide to use, make it sound hideous ... this track on it's own is going to sound like shit, but once you start adjusting the volume of your bass distortion track, everything starts sitting together very nicely.
Once you've adjusted the fader levels of both tracks to your ears' content, I normally send both of those to a single "Bass Buss" where I apply global EQ (do a cut in the lower sub-Hz where the kick's sub bass sits so they don't conflict with one another) and cut/boost as necessary. I'll also add some additional compression to "glue" the two tracks to one another a bit better and also add some limiting to really squash the bass even more so it stays consistent volume/dynamic wise ... if you need volume changes, automation is your friend.
You also have the option of using bass cabinet impulses (which you can probably find for free using Google) and loading them into a plug-in for Mac that loads convolution reverb impulse files ... check out
LAConvolver (it's free!) if you wanted that bass cabinet sound, but that's entirely up to you!
The best part about all that was that was all free! The only instance I would ever add an amp sim is to give the tone a bit more color, but if you carefully EQ/Compress, you really don't need one for bass. Hope this helps!
