SB600 is a great budget flash to go with your 16-85 lens. Can be found around $150. But it has some ergonomic disadvantages and also it less than "capable" in repeating fire and high shutter speed sync. The SB-700 is about the same weight and size, has much more advance electronics that prolongs battery life and reduces recycle time between the shots. Has awesome snap on color filters and can be found at $250 used and $275-$300 new.
My most used flash is SB800, followed by SB700, than SB910. I also always carry SB400 in my bag but it seldom get any use. I bought and later re-sold a couple of SB600s due to limitations I stated above. Think of SB600 as dedicated TTL external flash for up to 1/250 shutter speed. It quite powerful and works well for bounced flash photography as well as with Light Sphere. But if you ever need more creativity or faster shutter speeds - pick Sb700 or SB800 both under $300