Hi, I'm very new to Digital SLR camera. I'm planing to purchase an external flash for D40x. I know the SB-600 is great but I can not afford to get it. Would you advice me which one I should choose: 1/ Bower SFD35N iTTL Dedicated for Nikon Digital SLR cameras 2/ Nikon SB-400 If not Bower, which other brand name/model is good to buy at under $100? Thank you so much!