If you go with the S&W, plan on doing the trigger, I have heard a lot of " the trigger sucks" on it, and the Sig is DAO I believe. I have no experience with either, hopefully someone else will chime in.
The new Remington R9 is in your price range, but it's a brand new gun and not a lot of feedback yet. If it was me, I would save a few more bucks and look at a Canik tp9sa, new around $550, great pistol for the money. I own and shoot an FNS9LS, a used one would be in your price range, and you can't go wrong with it!
Bersa Thunder pro and a few of the Grand Power offerings will be right there price wise also, and don't forget the Girsan Regard, all of the pistols I have mentioned have a good rep, and are worth a look, in the end I hope you find one you love