Just keep CIS and throw in a couple of on-demand scanners for spyware. Me and a lot others recommend MalwareBytes Antimalware and SuperAntiSpyware. Both are free.
You can also install Avira Free, but disable the real-time scanning either in CIS or in Avira, although I heard they work nicely together :-TU
There’s really no need to pay for A-Squared.
And Melih is pretty much right (B)
Hope this helps.
as long as you are running CIS in proactive mode, it will stop pretty much all the malware infecting your machine anyway. So you don’t need a product to detect stuff… cos it won’t be able to enter your PC in the first place!