Nothing to be done about the side jacks, but the Spectrum is much easier out of the box than the C4. It's designed as an envelope funk machine that can be used without the deep dives typical of Source Audio pedals. I found it was awesome right out of the box. The knobs are designed to get you where you wanna go quack-wise. There are some things, such as inverting the envelope that you would need to go to the editor for, but once you do it, you could save it as a preset, and simply toggle back and forth. For many, 6 envelope filter presets is typically enough, and you could get Moog, Discombobulator, MuTron, Meatball/GR2, and tons of others from available user and factory presets. And it does the MuTron exceedingly well. I have no triggering or tracking issues with the Spectrum, where I had lots of triggering issues with the GR2, and some others I've tried. Also, the Spectrum includes optional phaser, as well as distortion, so envelope phaser is also available.
I hear ya, the Spectrum is essentially what I liked of the C4 once you bypass the tracker stuff and just use octave, fuzz and filter! I may get spectrum, though, I'm afraid the restrained envelope amount issue I spoke of earlier is still present in the Spectrum. Couple that with my side jack allergy and the motivation to Spectrum is low.