A thousand thanks for your very informative and speedy reply.
Q-1. So I guess I was wrong in thinking that the Nikon website said that the D60 could not handle a teleconverter?
Q-2. Any idea what the 14E and the 17E cost? And, can I use these with the Sigma lenses, or would I need a Sigma teleconverter?
Q-3. I run all of my images through Photoshop Elements. If I were to compare the final photographs from my Nikkor F4 to my Sigma 4.5 or 5.0, what would I see in terms of graininess? Would the Sigma have significantly more, just a tiny bit more, etc.?
Q-4. If I won the lottery, bought a Nikkor F2.8 300 for nearly $5,000, then compared its results with the Nikkor F4 (and the Sigmas as well), on a comparative scale of 1 to 10, how would you rate the overall results from each lens?
Q-5. If a dozen photographers, who all considered each other as semi-professional, got together to consider using the Nikkor F4 300, and the two Sigmas mentioned in your reply, along with appropriate teleconverters, would they as a group SERIOUSLY consider making these lenses their "lenses" of choice for bird photography? The reason I ask is that I don't know that much about comparative lens results. When I hang out in person or on the web with true semi-professionals later this year, will my work that came out of these three lenses have the possibility of measuring up favorably to theirs? I don't want to spend less than $2,000 if all that I can produce are amateur results. I've been a landscape and butterfly photographer for twenty years, and have, like anyone, picked up some skills along the way. This lens will probably be the last major photographic purchase that I make in my lifetime, being already 64. I'm hoping, with your help and that of other Nikonians, that it will be the right purchase.
Q-6. Given my age and all of the above, do you recommend my buying new or used, and from whom?
Sorry that this round took longer than the first. I would understand if you wanted to drop out.
Again, many thanks Marty, and best wishes in your own shooting.