I use an ERR RailSounds board in my conventional Williams GP9. I removed the Williams board and speaker first.
Consider wiring your loco in series—that will slow it down a bit.
I also used to use a WBB transformer, which was a rebranded Atlas, and it worked fine. You had to press the bell button for several seconds to turn it on and off.
Finally, I’m a fan of GRJ’s YLB. It provides a nice piece of mind, works well, and is easy to install.
—Matt