It was about the time Athearn switched the Genesis boxes from yellow to dark blue that they switched from the not so good MRC sound to Tsunami sound. Could be the box isn't an absolute indicator of the sound factory supplied. I would rely on the models description from the company for the type of sound.That's interesting, makes things a little more difficult, but I would assume the Soundtraxx Tsunami logo would appear on the end of the box?
I forgot to mention that the DCC ready model still is available in the dark blue box and is continuing also since the sound version has changed to the new Tsunami2 decoder.
I read a lot of negative comments about the MRC sound, and avoided it entirely, and saved money too. I have to say I haven't been overly impressed with the Tsunami 1 sound either - the horns are weak is one of the biggest complaints. The revised Tsunami 1 (called Economi) has supposedly improved on the short comings of the Tsunami 1 while offering a budget price. I have only a small number of sound loco's out of my fleet right now and it include 3 with QSI sound (mediocre), a couple with Tsunami 1, and an IMRC Cab Forward steam engine with Lok Sound. I've listened to some diesel Loksound and been really impressed so I'm looking forward to trying out those at some point or installing one in a silent diesel.
Supposedly Tusnami 2 is a big improvement over the Tsunami 1, but I haven't listened to any yet.