The 2004FS is basically a mondern day 4001 but the 2008FS is more of a replacement for the Simplex 4004, 8 zone 4005s, and the 5 zone 4006s but the 10 zone 4006 doesn’t have a proper successor. The problem with the conventional panels are that the biggest one is only 8 zones while the rest of the competitors have there biggest conventional panel being at 10 zones (with Silent Knight having a 30 zones). I think Simplex should come out with a 2010FS that can be expanded to 32 zones. Since it would work as a direct replacement for the 4002 and 4005. Or just a 2010FS would work as well.