I'd highly recommend Tenba ( www.tenba.com ) but I think they've stopped bringing in Tenba bags here. They are usually half the weight of the equivalent Lowepro bags, and much tougher. I used to own a Tenba P252 backpack, and read that they have been stress tested to 500Kgs! A bit expensive though, but well worth it.
Billingham bags are nice but way overpriced... better to get them in England.
My take on Domke - not worth it. I used to have a F4AF. The design was so bad, the flap used to leave two gaping holes on either side when slung on the shoulder. And it's just plain canvas, no water proofing. IMHO waste of money at Singapore prices.