Williams sound units - are they worth it?

[Winnipeg O gauge guy]

I just installed a Williams True Blast 2 sound unit in my Williams 44 tonner, and I was very disappointed in the tinny sound of the prime mover. It might be that the 44 tonners really sounded like that, but I don't know for sure.. I'm considering getting either the GP30 or the GP38 sound units, and I was wondering if the sound quality of these units is any better.