Full set of new lenses for my 7d

Hi, I see a few people suggesting the Sigma 150-500. I had one for a couple of days and got rid of it. Image quality wasn't too good at the 500 end. In fact my Canon 70-200 2.8 with 2X Kenko DG pro teleconverter was just as good if not better even when blown up to an effective 500mm. Its not too bad up to about 400 but limiting it to that is a pain.
If you are looking at L lenses you don't want the 150-500.

Iain