If you choose something like the SIG or the HK, you'll have to really practice on the DA/SA conversion thing.
On these "double action" semi-autos, the first shot is a long, revolver-like trigger pull, and each subsequent shot is a shorter stroke; you actually have a different trigger position. This has proven to be difficult for most folks to master--even after a considerable amount of practice. The tendency remains to pull the first shot low--sometimes WAY low, as you draw back that trigger.
I don't like this type of action for this reason.
I believe there are really only two semi-auto designs worth considering: The Colt 1911A1 in .45 ACP, and the Glock design. The Glock pistol will become the 1911 of the 21st century; it'll change little if at all as it's pretty much "perfection."
I own two 1911's and one Glock. With the correct 9mm ammo, you're going to have plenty of stopping power--so don't shy away from a good deal on a 9. Federal's 115 grain Hydra-Shoks, or my preferred, the Corbon 115 grain load, is quite successful on the streets in actual shootings.
This all said, my "house guns" are revolvers. I never have to worry about magazine springs being compressed for so long they don't function, or whether "there's one in the chamber or not." Wheel guns are quite comforting as far as reliability, too.
Dan