Matt,
The Soundtraxx drop in for the the Proto 0-8-0 isn't a Tsunami. It's OK, but there're a lot of sounds missing (especially once you've heard a Tsunami!). Even with the plug-in, you still have to install the speaker in the coal bunker, and drill a bajillion holes in the coal to let the sound out.
That said, you can't go wrong with a micro Tsunami, and if you're interested, I can tell you how to install the speaker. The "kit" that comes with the plug-in decoder is no big deal, basically some styrene strips and a baffle that you have to glue into the coal bunker.