Thanks for the feedback!
Here's the updated list.
I removed the 2.0 Extender and added the EF 17-40mm f/4L USM - I'll look at the Sigmas, but figure if I can get the Canon at a good price, it should retain it's value should I ever wish to part with it.
Any other feedback? please?
Canon EF 100-400mm f/4.5-5.6L IS USM
Canon EF 28-135mm f/3.5-5.6 IS USM
Canon EF 17-40mm f/4L USM
Canon EF 50mm f/1.8 II
Canon Timer Remote Controller TC-80N3
Canon BG-E2 Battery Grip
Canon BP-511a Extra Batteries
LowePro Camera/Computer Bag
Lexar CompactFlash Firewire Card Reader
Lexar CompactFlash Pro Series 80x WA 2GB