Correct supply to outdoor siren

Hi, I want to place my outdoor siren where my old Burglar alarm siren is. The main reason is all the old DC cables run from a convenient location where the old system was and go to the outside wall. I can't easily use the standard charger as the other side of the wall is a tiled bathroom.So, hoping to whack a transformer in where the old Burglar alarm box was, using the old circuit into out and the old DC supply feed out of itBit confused by the official siren help page for hard wiring, which mentions 12-40W but also do not supply above or below 12W.Does it draw 12W max, or can it be higher?Wondering if something like the below would be suitable.https://uk.rs-online.com/web/p/din-rail-power-supplies/2821710