Well your system is well up to the task.
I think you mean 1680GB not 1608MB, if that is the actual data size rather than the HDD capacity, then yes this could take some time.
It isn't just if there are any other AVs running, even if disabled they can cause issues and many also leave remnants when uninstalled. That is why I specifically asked about previous AVs, to see if we can't find a specific tool to ensure all remnants are gone.
One of the problems when avast finds one Trojan the sensitivity bumps up, but if you already had it on Thorough it can't go any higher, but I don't know if it would then also scan Archives (you didn't mention if you also selected archives ?). So it may well be better to stop this scan and do another one but Use the Standard sensitivity not Thorough without Archives. The problem being if it finds more trojans, etc. then it would bump the sensitivity.
If you haven't completely removed the Comodo AV element (but just disabled it) you should do so.
The other option is to do a selective scan (Folder Selection, rather than Local Disks) if you have a partition which has just Media files.