After a new camera bag

So I'm after a bag to replace as my main bag over my Lowe-pro minitrekker bag. Something that is more heavy duty in construction and support/comfort for when carrying a heavier gear - plus its regular storage compartment gets a bit full when trying to get waterproofs and lunch in their at the same time.

So I'm in the market for something larger and whilst I know that trying out is the best approach I'd like some idea of what options on the market might be the best to consider. At the moment I've my eyes on:

National Geographic Earth Explorer Backpack - Large
Lowepro Pro Trekker 600 AW

However I'm open to other suggestions.

As an idea of the kind of gear I want to transport I currently carry:
Canon 70-200mm f2.8 IS L M2 - 2*Teleconvertr - MPE 65mm macro
Sigma 150mm f2.8 macro - 70mm f2.8 macro - 1.4 teleconverter
Tokina 35mm macro
Canon 580EX2 - Mt-24ex
lunch - drink - waterproofs - other stuff

though I'm also after a bag that can easily take additions to that list - namely 300mm f2.8 so that the bag remains usable in the future.

Man! Just thinking about carrying all that gear has my lower back hurting!

The National Geographic bag is great! I'd also suggest that you consider Think Tank bags . . . perhaps the Airport Addicted bag?
http://www.thinktankph​oto.com …rt-addicted-backpack.aspx

Good luck with your hunt!

Ahh I'll have to keep a mind to think-tank and their creative names, though I think my local store does not stock them to try out. In addition the airport version appears as a good lens bag, but very flat in design so I worry that it simply won't take waterproofs and lunch inside