I'm so sorry for your loss, especially the sentimental stuff -- that is irreplaceable. We were burglarized shortly after we got married, and it was a terrible, violated feeling. Fortunately, nothing of sentimental value was stolen (correction: Big Tex's Very First VCR disappeared and he's still mourning that loss), but it was still unnerving.
We have a security system. I don't know how much good it would do in a real emergency, but it makes us feel better. We have two very vocal dogs. The only way they would actually stop a burglar is if he tripped over them (which is a very real possibility, by the way -- happens to us every day), but some people, like the pizza delivery guy, are actually scared of the happy hounds.
I think a security system is a good idea. If you get the kind that makes a loud noise, make sure it doesn't trip at the slightest sound or no one will take it seriously after a while.
Good luck. I hope they catch the guy.
Nina