I had a Nova System; sold it, got the L6 M9 used it for about 9 months, sold it, got the Nova System. The M9 had many more options, and you can order the signal chain any way you want, where the NS has a fixed effect order. The NS has less flexibility, and I think it sounds better...besides I didn't need all the flexibility in the M9...not a big effects guy, but I want my effects to sound good to me...the M9 sounds good, but the NS sounded great to me. IMO/YMMV
If you just want effects, I dig the Nova System. If you want 4CM, what about the M13? I would not be surprised by a new Nova at NAMM, but I dig the one I have...if it was a bit smaller, that would be better...like the case their vocal version is in...forgot what it's called.
BTW, I dig the Nova enough that it convinced me to get the G-System. I have both, but I also recently picked up a new Zoom G2.1Nu...(I've been digging Zoom for decades).