What good substitutes for saffron exist?
As for flavor, there really isn't a substitute.

Infusing saffron strands in a warm acidic liquid such as white wine will help extract the maximum flavor.

Whole saffron while more expensive than ground is a better use of your money as you know you're getting only saffron.  Ground saffron, while not usually found in stores in the U.S. may be sold by mail order or overseas and is usually less expensive because it's being cut and blended with other spices such as turmeric but won't have the same flavor.