Hardware Firewall, Software Firewall, Anti-Virus, Anti-Spam - is it enough?

I have a Linksys firewall which terminates my cable connection.

The wireless feature of the firewall is disabled as I have a wired 100 Mb network throughout the house.

There are four PC's in the house. Each is running Adaware, AVG Anti-virus, and Kerio personal firewall.

Can someone still break into the network and garner executive privelidges on any of my PC's? How would I further prevent against this?

My NAS is a 250 GB Buffalo Technology Linkstation. It runs LINUX, however, has a UI which provides little to no capability to tweak security settings. Should I worry about this?

I think I have covered the bases but am still worried about HTTP traffic compromising security - should I be concerned about this and what would I do to prevent it?

Hardware Firewall, Software Firewall, Anti-Virus, Anti-Spam - is it enough?house call

this free tool will give you real time protection to help prevent this and it plays well with firewalls and anti virus http://spywareterminator.com there is no 100% safe way to prevent an attack except not having an internet conected.

Hardware Firewall, Software Firewall, Anti-Virus, Anti-Spam - is it enough?matchless

some hackers can still give you viruses if you go into suspicious websites mostly porn websites, if you get spam or viruses on your computer, your anti-virus can still detect and delete them if it is upgraded.
Based on your setup I'd say that you're pretty well protected; far better than most.