Obviously the SB900 is the full-featured powerhouse, with a price to match. I have the SB600 and SB700. Both would serve you well for fading daylight and indoor use. I like the much more user-friendly controls on the SB700. If you're so inclined, you'll love the ability of either of these flashes to work remotely with the D7000's onboard flash in commander mode.
If you need the power and focusing of the beam out to 200mm field of view, the SB900 is just the perfect solution. If you are primarily using fill flash with primary subject nearer to you, the SB700 will do almost all of what its big brother does. I have two SB900 and a Sigma EF530 Super. For normal use either model does fine despite the wide price difference. When you need to use a flash closer to its limits or using a power robbing modifiers like softboxes, or have more control of the light due to wider and narrower focusing range, the SB900 is hard to beat. My only quibble is that the flash Compensation value display is tiny so hard to read in the dark or from a distance. That is the only complaint, everything else makes the SB900 the best flash of its type. The only one that in some cases is better(more power and staying cooler in rapid shooting) is the much more expensive Quantum flash with their external battery pack. Stan St Petersburg Russia