I have the baby slingshot, the 100AW and it takes DSLR plus 17-70 lens, telephoto zoom 70-300, 50mm prime, all in the main body, plus 'folded' Sigma flash in the top pocket. Tight squeeze though and not much extra room for spare batteries, filters, etc.
I have an Orion Trekker II and a Kata R-103. The Kata is superior in every way. For less kit, I think there is an R-102 or R-101 (and possibly various other rucksack type bags by them). I got mine from Morris Photo, which was the bestest price I could see at the time (and it came very quickly).