With a 100,000 difrent brands, and write speeds on the market how do you know which to buy? I just purchased a 5d and only have a 2 gig card, which for what I do has always been fine. I'm going away on a 1 week trip and am going to pick up a 2nd card...should I go after a 2,4, or 8 gig card? And how do you know if it's fast enough? Any advice is helpful

