Matt,
My price observation is based on looking into sound decoders for Kato N-scale P42's and F40's. The great thing about Loksound and Digitrax is that the sound files can be loaded for a specific loco. Thanks for pointing out the Loksound prices as it made me look at them again. I see they have a sound file for METRA MP36PH which is also one of my N-scale engines. I'm thinking now that the Select Micro may be the way to go with that engine.
I have also used Digitrax sound decoders with edited sound files in modified 'streets vehicles running under DCC.
Larry