I'd throw the Sigma 24-70 HSM f/2.8 in there too if you have the money. It's a little wider than the Pentax 28-70 and it has gotten good marks when going against the heavy hitter 24-70 lenses from Nikon and Canon (it's also relatively compact compared to the Canikon offerings).
I can vouch for the DA16-45 as being a great lens if you go that direction. The lens speed won't make as much of a difference if you're planning to use a flash. I tend to like to limit my flash usage, but I should probably get over that. The DA17-70 is essentially the same as the DA16-45 optically from what I understand. (maybe slightly smoother bokeh? Don't hurt me if this isn't true) The DA17-70 is also SDM, though, so if you're worried about that I'm sure it won't help.
Peter Zack shoots weddings professionally and posts here and I think he's recommended the DA16-45 as a consistent performer before.
I probably won't be able to quell your SDM fears, which are understandable, but I can say without a doubt that the DA*16-50 saved my butt during a wedding I shot last September. I tend to favor primes, and still used them during parts of the wedding, but when things sped up it was so great to have one lens I could rely on.
Some examples from that wedding: