I use this method ever since I first read it in TAG (Journal of the AGA), and I can't say enough how great it is. The amount of Co2 production is so much higher.
By the way, Ammonium Sulfate is also known as Yeast Nutrient. I also find that a bit of room-temp juice (NOT OJ which seems to create bad bacteria), but like Ocean Spray Cranberry juice, makes the end result smell so much better
I've found a grocery store brand of protein powder that works fine, called Adkins Advantage, $8 for a big container. I liked Spiruteen the best, but it was a bit expensive to use.