Crystal Security is a really powerful cloud AV. Since Comodo Internet Security had relatively weak AV I was actively looking for a companion AV that offers good zero day detection and found Crystal Security does the job fine. Currently I am experimenting running Comodo Internet Security with Crystal Security. So far so good. Needed to test a lot more to ensure its trouble free operation
In such way that you can have this program by alone or a companion, enough multi engines covered to detect any matters of threats. A rare case if all AV's engine did not detect them which makes CS protection module bypass but again unlikely.