Originally Posted by CPRich

My mistake on the Sigma "nomenclature"

The 50-500/6.3 is the Bigma

The Sigmonster is the 300-800/5.6 - perfect for what you need, but $7K. If you're spending that much, I'd go for the 600/4L plus 1.4TC

And then there's Sigzilla - 200-500/2.8. A 2TC is included in the purchase price to give 1000mm and retained AF with f/5.6. But it's projected at $8-10K and 35lbs.