There's a quite a bit of this sort of threads from various sub sections of this forum that talks about bags? But I guess this one applies to Pentax Equipment since TS is talking about K100D + Dual Kit.
This was my first setup when I got Pentax back in 2005 (K100D + Dual Kit)! Back then I use the Photorunner from Lowepro. Fits everything in with blower, lenspen etc.
Personally, I prefer a camera bag, best if it's understated kind. I have a domke f-3x that looks like kiam chai so no one really takes a 2nd look -
Neoprene is good too, just that I felt it's all jumbled up in the bag, and something very difficult to rampage through the bag when you start putting in your small umbrella, some visitors brochures, a light jacket, water bottle, passport etc.