|Avast is OK for a free AV but it has gotten a bit annoying on its reminders, telling you it has updated, scans at start up or even wake from sleep, etc.|
My preference is Webroot Secure Anywhere. It is a pay for AV, I believe it has an available free trial period, it uses system resources respectfully (you never feel any slow down when it is doing a routine scan), Manual scans are fast and efficient, and unless it finds something, you rarely know it is even there. Don't in my opinion go with more than the basic antivirus program, it is not necessary. Combine that with occasional manual scans with Malwarebytes and you have layered protection.
Avoid McAfee and Norton as both are system resource heavy and I feel that they are overpriced and based on an older technology.
You have to be a little bit crazy to keep you from going insane.