[MrIcky]

Pretty much all of the guns suggested are great guns, but as others have suggested there may be some standouts for your situation. Others have made the same suggestions, but I'm going to expound a little.

I'm assuming you and your wife are not super familiar with guns. The only gun you own with minimal training (say 1 NRA class) probably should not be a single-action automatic (H&K's, Sigs, Springfields, etc). If there is a bullet chambered with the hammer down, then the first shot is double action and the 2nd is single action (which significantly changes the trigger force required).

The goal is to have a gun that fires in a very consistant manner so you rely on muscle memory to do the fine actions involved in firing. This way your mind can concentrate on proper call out and target identification.

My recommendation would be:

1: A shotgun, preferably a 20 gauge. Bigger is not always better in home defense.
2: A double action revolver. .38 is a good all around gun. .44SPECIAL (not magnum) is good as well.
3: If you really want a semi-auto- I'd go with a glock because it's pull is consistant between the 1st and all subsequent shots.

Your goals for home defense should be:

Best Sight Picture
Maximum Stopping Power
Minimum Overpenetration

You also need to realize home defense and concealed weapons have different goals and therefore different guns make better choices. Home defense training focuses on call outs and positioning with good knowledge of the angles of your home in hopes of making the bad guy go away. I prefer my home defense weapon to be intimidating rather than stealthy. I have a railmount flashlight on my gun. I would rather get shot for being too slow to shoot and having a flashlight then accidently hit a loved one. Everyone who attends an NRA inside the home class is always stunned at how much stuff even a moderately powered bullet will go through.

People have a misconception that hollowpoints get stopped by walls. Instead they cookie cutter through gypsum which blocks the hollowpoint so they don't expand right. A 9mm can pass through several interior walls without a problem. Fluid is what expands a hollowpoint. Even trained people are horrid shots in tense situations- and if you have people in your home, missing the intruder is a bad option. The best choice is to scare away the intruder without a shot.

For concealment your goals are:
Small size
Protected from snags/access
Adequate stopping power

Most concealment encounters occur within 5 feet. Aiming and sight pictures aren't a real-factor. Nor is target identification. My favorite concealment weapon is the S&W airlite titanium. No sharp corners that can snag and .38 is a good all-around caliber. You can spend twice as much time talking about proper carry positions and holsters as you do about what gun to choose for concealment.

Sorry for the long post.