Used 80-400VR lens, help me to choose please

Thanks very much for the responses.

I have been looking for a lens to photograph Birds and Wildlife. I do have 70-300 VRII, but I find the reach insufficient. If I crop too much, the resolution suffers.

I have considered a number of options (after discussing here and elsewhere) like Tamron 200-500, Sigma 150-500 OS and AF-S 300mm+1.4x TC. The third option seems to give best IQ for the price.

Now I found that this lens gives a very good result at the longest end if I stop down to f8, better than 70-300VRII at the longest end. And if I get it cheap, I can use it for some years then sell it off to buy upgraded prime lens, which is my final goal.

Thanks again.
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