ok I will bite on the caliber war. I own:
glock 17 9mm
H&K USP compact .40
Sig p220 ST .45
Remington 870 12 gauge
an AK and a few others.
Since this is your first gun I would vote 9mm. Mostly because ammo is cheaper and you are going to want to practice as much as you can. Shot placement is the key no matter what major caliber in a handgun. That said when I carry I dont carry my 9mm and choose the .40 and .45. I have been shooting since I was a child and 100% confident I am going to hit what I am aiming at no matter which of my platforms I am carrying at the time.
The reason I recommended the FN's FNX (perfered) is because you are left handed, gun has a decocker, and they have a safety. Also its in your price range. As much as I love my Glock I cant recommend it to a new gun owner for the simple fact it does not have a safety. Same thing with my p220. I am not saying they are bad guns far from it, I am saying the features dont lend themselves to new gun owners. Feel free to flame me here but I dont care and stand by my opinions. Sig, Glock, S&W, H&K, FN, and Ruger make wonderful guns. As I read in another post stay away from Taurus and kel-tec.
The real question is: Is the main duty for this gun home defense or range gun. If you are serious about the HD thing skip handguns and go get a Remington 870 or a Mossberg 500 or 590. Done. If you want a range gun get a good solid 9mm shoot the piss out of it and enjoy.