The IDY designation is not used by the yeast producers for their yeasts sold at the retail consumer level. It is used for their professional customers. However, yeast sold as "bread machine" yeast in supermarkets is really IDY. Also, the RapidRise yeast from Fleischmann's and the Quick-Rise yeast from Red Star and the SAF Gourmet Perfect Rise yeast from SAF are all forms of IDY. All of these yeasts are sold at the consumer retail level. Many of our members buy IDY (and ADY as well) in one- or two-pound bags/packages from places like Sam's, Costco's and BJ's. They can also be ordered online from places like amazon.com, PennMac (http://www.pennmac.com/
) and King Arthur, although their prices will usually be higher and include shipping costs. If you do a lot of baking, you should buy the bags of IDY or ADY because of the significant cost savings over the three-packs or small bottles sold in supermarkets.
Whether you use a pan or a stone is largely dictated by the type of pizza you want to make. For example, NY style and Neapolitan style pizzas are baked on very hot stone surfaces. Some American style pizzas, such as sold by Papa John's and Domino's, are typically baked on either pizza screens or disks. Other American style pizzas, such as sold by Pizza Hut and Little Caesar's, are typically baked in moderately-deep pans. Cracker-style pizzas are usually baked on a stone surface but flat pans, cutter pans, and disks can also be used. Deep-dish pizzas are baked in deep pans. A pan will produce a different bake than a pizza stone, although good results can be achieved with either. For best results, however, the pan should be a dark pan, either one that has been seasoned and darkened from long term use or a dark, anodized pan. Most of the recipes you will find on this forum will instruct which baking medium to use.
The best position in the oven for a pizza stone is usually determined from experience. Different ovens produce different results. Some people get the best results putting the pizza stone on the middle oven rack position. Others get the best results putting the pizza stone on the lowest oven rack position. I would say that most members use the lowest oven rack position.