Here are two of my O Scale Alco's; an Atlas QSI fitted RS1 and a RS3 that is currently being fitted with a Loksound V4.IMG_0033.jpg
Is the RS3 a Weaver "China Drive" one? The decoder looks like a Loksound XL. Have you got the latest version of the sound file for the RS3? it is better than the earlier version.
Nice to see some more O Scale modelling.