The question of software really depends on what sound you are going for and the style of music you play. If you are going for more of a "synth bass" sound, as opposed to a sound which mimics acoustic instruments, you could look into Arturia's Mini V, which is a soft synth version of the MiniMoog. It is a VST plug in, so should work with most DAWs.
I honestly have never used it, when i did keybass I used hardware, specifically a Moog Little Phatty. But I've heard good things about this software, and it only costs $99 on Amazon right now.