Thu 24-Jan-13 01:26 AM | edited Thu 24-Jan-13 01:29 AM by dm1dave
This can be an expensive question. So, not knowing how big the bank is...
The sigma zooms are a pretty good option and the price is good. The 150-500 will give you nice reach and very good image quality. The downside is the small max aperture at the long end it can be harder to keep your shutter speed up.
The Nikon 300/f4 with a TC14E is usually a highly recommended lens in this forum. Image quality is outstanding. It could be a bit short on an FX body but should work quite well with the TC17E.
If you could spend more the Sigma 120-300/f2.8 with the Sigma 1.4TC is an outstanding lens. You can save some money by looking for the older non OS version. It is a bit difficult to handhold. The newer OS version should be better for handholding. This is a very good alternative to the Nikon 200-400 at about half the price.