I just purchased the SX20 IS and the online store called me and said I need to use a class 10 card in the camera. I'm pretty sure he is full of you know what but can anyone confirm that a Class 4 (which I have and us in my S3 IS) or 6 will work just as good. I don't plan to do a lot of fast continuous shooting since they camera doesn't really excel at this anyway. I'm not a professional. Thanks.