you have a few options.
if you plan on regular on camera flash and wont need anything more. meaning, creative wise, you wont want to do off camera flash, use them with umbrellas/softboxes with wireless slaves or use them outdoors for fill light and HSS, then an Sb600 will be fine. or a yongnuo 565 467II 468II are just fine. there are other companies like triopo, neewer, sunpak, nissin, sigma and some others. you can use any of these flashes I listed as off camera flash with a wireless slave and the 565 and Sb600 will work with your cameras built in flash to fire remotely off camera if you want to get creative. personally, Nikons CLS sucks ***.
if you would want to take your photography up a level, down the line (wow that sounded corny), then the SB700(330) or even a used SB800 (250 used)will be great. yongnuo have the 568 (175 shipped) flagship. and there's a great flash from phottix. the mitros (300)and mitros plus (400 the plus has wireless triggering built in) it has all the bells and whistles of the Sb-910 including the power and refresh speed at almost less than half the price and 2 years warranty. personally, if you really need extra warranty, get mack diamond warranty for $50. its 3 years and its like an all risk insurance. if it falls and breaks, they fix/replace it. if you take it to the beach and it corrodes and falls in the water they fix/replace it. since I work with my equipment, I dont buy a piece of gear without it. you have to decide if you need or dont. the flagship nikon is the SB910. I think its too much flash for you if its a day to day, a little family, friends, some studio work and the like. $550 bucks is not cheap.way overpriced IMO.