My 9, my ONLY 9, is a Hi-power. It fits the criteria to a T, until you toss in the single stack rule. If I were forced to get another 9 in a single stack, I would look a little harder to find a Springfield EMP. Small, relatively light weight, and a very good looking gun, though I admit I have yet to shoot one to date.
I would go with a Colt LW Commander 9mm . 9 rounds single stack light weight and is a 1911. If you are going to run a million rounds a day get the steel one. Either one would serve you for a life time. One of my carry guns is a LW Commander 9mm .
I would have to agree with WestSider. The M&P 9C at only 1.2" thick gives you excellent performance vs. size. It is double stack but it's size allows for both CCW and HD. The Shield is single stack and would be fine for CCW but for nearly the same size and money the 9C is just so much more flexible. 10, 11, 12, or 17 round mags. Just something to consider.