What you're running is going to be fine, when the paid subscription runs out then you can switch to Avast and save some money.
A little paranoia is a good thing but don't take it too far. Otherwise you'll never turn your computer on.
ANY virus protection program can let you down, the defense against computer virii is reactive, anytime a new virus surfaces a few people are going to get nailed before the virus protection programs are updated to defend against it.
Make your backups. You can lose stuff even without malware. I lost the hard drive in my laptop this week to mechanical failure, (sounds like a chain saw), luckily I have the data saved elsewhere.
I would say that Kaspersky is as good as any of them. Personally I would prefer it to Symantec, as I have seen far fewer conflicts with other software.
You have probably noticed that a lot of attacks these days are via applications, so it is very important that you remain fully patched: This is the tool that I use (it is free):
Nod32 seems to have good ratings from some people. I personally rarely think about AV, and on Windows, whatever I can find that isn't back doored I'll usually be fine with. And then I use Spybot too.