RE: S&W Sigma or Glock,M&P,XD
Glocks are nice reliable guns, but I don't care for them. I have shot a few. I suggest buy the XD. I have one in a .40, and will be buying one in a .45 when I return from the Sandbox. If you don't mind shopping around, you can find an HK compact used for the same price range. IMO, that is a better gun than those listed. If you have to have it new though , you will spend 7-900 for one.
good luck