Thank you for the comments. Here is a lens comparison.
Canon 100-500mm & 1.4x at F10, 700mm, 1/2000, -1.7EV, ISO 1600.
Sigma 150-600mm, F7.1, 600mm, 1/1600, -.7EV, ISO 250.
I am have a hard time Spending $2,700 for the Canon lens & $500 on the 1.4x??
Sigma tells me their 1.4x is better than Canon’s, I will have to rent one to find out.