Doubtful that you'd notice much difference on the current tier. If you upgrade speeds then yes definitely go for the CM600. The 24x8 would be limited to either 16x4 or 24x4 depending on your area.
You mention "stability" as a motivator. Are you having dropouts or signal issues now? If so, a new modem won't fix that.
Ping and latency are generally independent of speeds and bandwidth. For gaming and other latency sensitive apps (video conferencing, etc) having the extra bonded download channels could help if your connection is maxed out, but upload won't change. I think the bigger indicator of latency will be the number of hops to the destination server and how congested each leg is along the way.