Thx for the info. Even if the taste isn't much different I just enjoy growing my own food so that's not a huge issue for me.

Does anyone know of local nurseries that sell certified seed potatoes here in Phoenix or do I need to order them from a seed company?

Just an organic potato cut into cubes to capture at least one 'eye' in each cube will work.

The organic ones from Sprouts always sprout in storage for me so I'd bet they'd be a good place to grab some

Find organic seed potatoes at groworganic.com or potatogarden.com. (per Catherine the Herb Lady) You can also call the local A&P Nurseries and see if they have any crowns yet. If you decide to grow from store bought use only organic potatoes as normal potatoes in the store are usually sprayed with a chemical to help inhibit sprouting.
As you can imagine seed potatoes are hard to get this time of year as most potato growing regions are in winter. But those above are exceptions. Be sure to request immediate shipment because they should go in the ground starting early January. Even late Dec. if you live in the Phoenix area.

Lastly, I see mixed results with potatoes in a bag. One issue is their drying out faster due to the wicking nature of the fabric. So make it a big bag. Potatoes are excellent soil cultivators and it seems a pity to me not to try to break up mounded soil around here.

http://forum.vpaaz.org/forum/topics/sprouted-red-potatoes-to-share?commentId=2008067%3AComment%3A286471

Fun discussion, thanks for starting and participating in it. I do love me some good potatoes, hah!