Id love a 600mm. How many arms and legs are we talking? Im sure after a year of saving I may be able to afford 2 more good quality lenses. Also, both the lenses mine came with say DX on them. Is the D3100 not a DX body?
And yes, Im shooting in just RAW.
Yes, the D3100 is a DX body, but there are also FX bodies which are the digital equivalent of 'full frame' (the DX bodies are 'crop bodies' and the focal length is usually multiplied by 1.5 when used with a crop body, so your 200mm is really acting as a 300mm lens on the D3100 I think). Some lenses work better with DX, some with FX.
Turns out the 600mm might work fine with FX, but your D3100 is going to look tiny perched on the end of this beast http://www.amazon.com/Nikon-600mm-T...8&qid=1382950280&sr=8-1&keywords=nikkor+600mm
I don't know if you'd need to lose an arm and a leg in order to pay the $10,000 cost, or lose an arm and a leg just to carry it out around.
You could always spend ten times less and get a Sigma 150-500mm http://www.amazon.com/Sigma-150-500...F8&qid=1382950389&sr=8-2&keywords=sigma+500mm, or if you wanted a wider variety of focal lengths, there's the Sigma 50-500mm which is a little bit more http://www.amazon.com/Sigma-50-500m...F8&qid=1382950423&sr=8-5&keywords=sigma+500mm