Dont forget installation. Im looking at getting FRPP HotRod cams for my GT, they do not require new valve springs, just pop em in. However its still $500 in labor on top of the price of the cams, so...
Cams will change the duration that your valves are open and closed for, longer duration generally will net you more power in teh mid and upper range, the downside is the rough idle but depending who you ask it may or may not be a bad thing. you car will shake a bit at the stop lights but the rumble sounds BAD ASS!!