Atlas used QSI, they sound very good IMO, almost as good as Soundtraxx Tsunamis.
Be careful with Athearn sound, the older sound units all used MRC, not the best sounding and hard to program if you don't have an MRC DCC system. The current Athearn sound units use Tsunamis and that just kicks butt! Soundtraxx offers drop in sound decoders for most of Athearns previous sound releases, so if you want an SD60I with sound, get the non-sound one and add a Tsunami. The newest release of the MP15AC will have Tsunami sound out of the box.