I have both a
Sig Sauer 2340 and a
Glock 27. Both models are .40 caliber. I like that because they're more effective than a 9mm and not as overpowering as a 10mm. I can't be happier with either of them.
Both have great trigger action and are very accurate. I'm not the best shot in the world, but I can shoot about 4" groups at about 20-25 yards on both (personally, I can routinely shoot tighter groups with my Glock...might have to do with the trigger pull being smoother and more consistent).
The Glock 27 is easier for concealed carry (though I'll carry the Sig if I'm wearing the appropriate clothing), but wouldn't hesitate to use it for home protection--it's certainly not too small.
Since I have two young kids, I have a quick access gun safes for each (each is in different strategic locations in my house for tactical access if the need arises) made by
Mossberg (unfortunately, this model is no longer being made). To gain access, one needs only to enter a six digit code and the lid automatically pops up. This only takes a couple seconds. They have audible alarms if someone's been tampering with the keypad, trying to gain access when they shouldn't. The alarm sounds if three consecutive wrong codes have been entered. Then it gives me a special tone when I next gain access to alert me of the unauthorized access attempts. It also has a lighted keypad and dim red light for seeing what you're doing in the dark. I think gun safes (or other locking devices) is mandatory and responsible for gun owners (especially those with kids).
I did a lot of research before buying my handguns and both of these received great reviews. Having shot many guns over the years, there's a variety across the board of everything from great guns the crappy guns. There's some handguns that are better than mine, but a ton that come in below. In my opinion, though the Glock is a relatively ugly gun (its appearance has grown on me), it possess the best bang-for-the-buck out there! Also, I'd recommend just about everything from either Glock or Sig Sauer.
As you've read, there's many opinions on which type of handgun is better--revolver versus automatic. I earnestly come down on the side of the automatic. In my opinion, if one's found a quality and simple functioning DA (double action) or DAO (double action only) handgun, it will routinely out perform the "wheel gun" all the time. It's easy to find guns with clips that will hold more rounds than a revolver. Jamming issues have been virtually eliminated. Though supporters of revolvers will say it's just as fast shooting a revolver than an automatic, I believe that for novices and those with moderate skills (which is by far, most of us), it's easier and quicker to accurately shoot an automatic. Also, look at the military and law enforcement choices for guns...automatics, hands down. There's many other reasons too, but I've become much to verbose here and I'm getting tired and need to stop typing.

[But I'll keep on going anyway...]
I'll easily echo the taking of gun safety and training classes for everyone! Without this, one will accidentlly put a round though a wall of their home, shoot off a toe, or put a round in their best friend (we've all read the news stories). I've had gun safety courses and proficiency training...but one cannot have enough. Also, regular shooting and training is essential in being both safe and proficient. So often have I heard of those who purchase a handgun and either decide they have all they need to defend themselves (a handgun) or they'll take a course or two and decide they have enough for their entire life to defend themselves. These are huge misconceptions and not nearly enough people that are ready to shoot their gun in an emergency situation (not to mention on the shooting range).
There are certainly many wonderful handguns out there and there have been a number of wonderful suggestions here already. I'd suggest that you stretch a little higher than your $500 maximum (for everything). Your handgun alone with be about $500 for the minimum of something that shoots well and is reliable ($200-300 more for something even better...without being "spectacular"). Your other supplies (depending on how much you purchase) will run a minimum of $100 and could run several hundred. If you ever think of possibly carrying your gun, a quality holster is needed. I have leather
Galco holsters for each and several other holster for my Glock.
BTW...next on my "to buy" list is a quality 1911. Though
Colt has several that interest me, I'll likely go with
Kimber (many of those have strongly interested me!), or maybe
Para Ordinance, or something in the range of those. I'm open. It's way too easy, though, to spend a mountain of money on a quality 1911.
Best of luck and make sure you let us know what you've finally decided.
Below are pictures of my handguns, holsters, and gunsafe.