I would personally get a bag that just fits your travel necessities. The camera body + lens and 2 other lenses at most. Add flash, batteries, filters and charger. It would keep your bag light and if it does get stolen, you wouldn't lose your entire camera collection!
So get two bags. One for your outdoor/travel bag and a pelican or hprc hard case for the rest of your gear.
I have to agree with this.
If you were looking for cheap bag that wasn't too bulky or overly expensive there are some good ones on ebay (china direct) that actually fit a fair bit of gear in them.
i bought this one...
...just before xmas and it fits Gripped 60D, Gripped 5D2, Tokina 11-16, 50mm 1.8, 50mm 1.4, 24-105, z finder, lens gears, Rode video mic, LED light panel, Gorilla pod SLR Zoom, Zoom H4n 8 Spare LPe6 batteries, SD and CF Cards, iPhone and random bits and pieces (intervalometer, AA + AAA batteries, Markers etc)
AND a 13" Macbook Pro. (in its own 3rd party sleeve/cover)
Weighs a ton but its convenient having everything that i need in an easy to get too location while on a shoot.
Heres a few links to a couple of styles they do. (ignore the capacity ratings they give as they are way under estimated)SatchelBackpackGirly
Before i used these bags i was a Crumpler
user but as great as they are i can not justify the expense of them anymore.