For bass (and as an all round synth) I'd strongly recomment Novation's V Station. It sounds great and has a good set of effects too, including a great sounding distortion. It does a lot of my lead sounds as well, and it does them very well indeed.

If you want a synth that *can* be easy to use to get random techno-y sounds, just get this, it's a free synth called Crystal. It is a cpu hog, but you can freeze it in Ableton and flatten down to an audio clip instead.

Crystal Synth

Happy music making dude :)