Well... maybe Plaits is the way to go... but let me point you in another -possible- direction. Plaits is a digital module with various different waveforms to choose from. It's a good choice if you want some "bread and butter" sounds as a source.
A "through-zero" oscillator may give you some interesting waveforms and modulation to add to your arsenal. I bought an Intellijel Rubicon 2. It also has lots of interesting modulation sources. You can use it as a standard VCO. But things can get fairly interesting when you throw some modulation at it and use it in non-traditional ways. It also runs in LFO-mode so you can create some very interesting LFOs as well.
Noise Engineering offers some interesting digital sound sources as well. But you'll have to pick and choose carefully as some of them might be a little too aggressive sounding if you're looking to pair them with another sound source.
No matter what sound source you go with, I'd definitely add another mixer module as you may want to mix your oscillators before you get to your filter and then possibly after the filter with effects.