>The D600 specs that caught my eye were the Dynamic Range. >The specs I saw indicate that the Dynamic Range of the D600 >are very good from about 200 ISO through 800, and they were >much better than the D7000.
Just remember that you can't interpret a measurement of the D600 in FX mode and expect it to apply in DX crop mode as well.
It turns out that most of the advantage for FX cameras comes from simply having a 2.25x larger sensor, which collects 2.25x more light. It may be unintuitive to see how this relates to dynamic range, but to generalize, more light = more signal = better signal-to-noise ratio = less noise = cleaner shadows. It's in the clean shadows that you find the extended dynamic range. Shooting in DX mode negates this advantage, and it's unfortunate but true, pixel-level quality hasn't improved much since D90.
Given that lenses hold their value over time, and camera bodies universally do not, buying FX lenses first means in the long run you'll pay less for your kit (likely pay less for a D600 in a year or 2) and shooting DX lenses in the short run, you're not going to see any difference anyway.