Sorry but no.
I run NOD32 at home.
This is on my i7-950/12GB machine.
The overhead from my AV software is nothing and I mean nothing.
I can run any number of benchmarks, tests with both the AV switched on and switched off and my scores will be the same.
At work and on my wifes machine we run Sophos and the same is true.
There is no drop in performance on my wifes machine.
Now I haven't tested every single machine at work running Sophos - but I'm pretty sure that if there was a performance issue some of my users would be telling me by now.
I stick by my statement - there is next to no overhead from resident AV these days.
Also - what exactly was the point of linking to an article 3 and a half years old??
I also fully question their results - 177% disk increase....umm......no.
Going by that post you are what, a junior admin? AV has a clear and distinct impact on many aspects of a systems performance.