Roundhouse Bill posted:MTH may never build another S Gauge engine.
That was my first thought, as well. Unless you run O as well, that is a lot of coin just to unlock a couple features on two engines. You cannot buy the Proto Sound decoders to retrofit other engines, either, unless that has changed recently. I know you don't care for DCC, but it is a bit less to get into (~$300 with wifi) and you can fit a decoder to most any loco.
Brendan