Just found out that MRC Sounders are in again. This version has SD-45 and MP-15 sounds, so good for those K-line switchers and probably any of the turbo EMD locos built from the 1960's through the 1980's. The volume should be louder - Frank said it was a software change. The remote control is also in stock. To get the OGR Forum price you must contact Frank direct at rrtech@modelrectifier.com or call him at 732-225-0964. He also said if these sell, then they will offer more types of locos.
Unfortunately the price of the sound board has gone up like everything from China, but the remote is still at the old price. (Both are still a lot cheaper than any other).
I'm getting one for my MP-15 and maybe more for my MPC SD-18s.
If you aren't familiar with these... they have a simple 2 wire hook up and give you several choices of horn sound. The remote also gives you coupling, air release and dynamic brake sounds.
John