Hey guys. I have been looking into some gear lately and have noticed some talk of using better flash than the flash that comes on my D40. I am relatively new to photography and mostly shoot landscape, but my wife likes shooting people and especially babies. I was wondering how helpful/useful a speedflash like the sb400 or sb600 would be. Also, if a speedlight is necessary, would you recommend the sb-400, the sb-600, or something else altogether? I currently am using a D40. I don't want to spend a ton of money on a flash, but also don't want to wish that i had more power and options in a couple of months if i went with something basic like the sb400. Any recommendations and information would be great! Thanks.