Having many antivirus scanners is fine.
Having a layered protection system doesn't work conflicts with many things running at once can make things interesting.
Now there is probably a way to handle this without issues but I have maintained several family systems loaded with layers of antispyware, antivirus and other things.
Lets just say, that all this stuff slowed things down a lot.
Not to mention all the other issues associated with all of it.
I had to remove all the antivirus and security, and then because I couldn't reformat and reinstall those systems.
Now I have heard of clam win there is supposed to be a module called centinal which is supposed to do the protection thing.
I havn't had time of late to try other scanners though its a combination of my laziness, the fact I get easily distracted and life in general and more towards the second of the 3 things.
It does not help that I can get distracted quite easily even in real life outside the online community.
I sometimes can stare at the wall for hours on end and wander why time has past.
Msse was good now its not so good anymore.
The viper sounds good, if you can afford the cash for full time protection for each system you do then its fine.
However with subscription based security you can only manage 1 or 2 packages which is why I havn't moved just yet.
I have also had my bad experiences with security programs both free and commercial everything from bad programs to misconfigured programs to false positives and such avg did this a lot especially when I converted text files from Linux to windows.
And as a result my confidence with all security programs bar msse which has not much protection but does not bug me every 5 minutes is the deal.
Some day I will actually do something about it but I never seem to have enough time to do things even when I do if that makes sence which it probably doesn't.