Avast = Free
Mcafee ENTERPRISE = £££££££'s
You get what you pay for.
But on another note: I dont have the time to go through your list, but of the top of my head,
QLowZones-4 trojan - is a Trojan that was discovered in Jan 2004, Proxy.Raser trojan
late 2005 - I just can't beleive you when you say avast did not detect them.
I have a paid copy of AVG and haven't had any trouble with the 30 workstations using it. I still use a combination of firewall; malware detection and common sense to help.
You could also do a combination of dual booting, one OS for regular things and the other OS for work. Make restricted users and USE them. I know so many people that surf the internet with their Admin account when they could play it safER by using a restricted account. Also, make some insane passwords for your admin and service acounts.