I'm a beginner. I have a Nikon N75. I take pictures of family, family on vacation, and outdoor shots. I can't decide which speedflash to get - a used SB-28 from ebay (around 170 bucks), or a new SB-50DX which would run around 120 bucks after the current rebates. I understand that the SB-50 is not as powerful, but do I really need it? Any thoughts would be appreciated. Thanks.