I have recently bought a Think Tank Streetwalker Pro backpack, great piece of kit, very comfortable, it can take around 9-10 pieces of kit. It takes:
EOS 6D with Zeiss 21 ZE
EOS 6D with Canon 35 f2 IS
Canon 100 macro IS
430 EXII flash
Plus Lee filter holder and filters for above lenses, and assorted accessories (charger, extra batteries and cards, etc).
I have considered the Gura Gear packs, but where I live (Portugal), to order one is just too expensive (more than 400 euros).