What program do top designers use to make silk screening or prints on t-shirts?

What is a good program that I can use, money isn't a problem so anything. Not a printing machine just a program of some sort to actually create the design on. I like the prints that Diamond Supply Co. uses and also The Hundreds, but what programs do they use? Is Photoshop CS2 or CS5 good? I nned something that will create high quality text and images. Thank you in advance for your help!