United Plugins have released a number of audio processing plugins which I've found useful over the last couple of years and their latest is very handy one for bass, designed to offer an easy solution and clear options for processing bass sounds in any DAW.
I was lucky enough to be offered a chance to trial the QuickBass plug in before release and I can confirm it's useful, well thought out and user friendly.
I particularly enjoyed exploring the doubler effect (especially on fretless) which differs from more standard modulation effects.
Adding Sub is always a good option to have of course and the saturation ranges from subtle to more than enough.
I have contributed a number of presets, which are hopefully useful places to start when searching for a sonic option on bass or perhaps just exploring low end possibilities. A lot more information can be found on the link below:
There is currently a free trial version, and an introductory discounted price, so it's certainly worth investigating.