I have no issues with Avast!. And your CPU and mine are about the same. I should also point you, it’s most likely you have “Adware” sitting on your system as I have not once seen an Advertisement from Avast!. I should also point out, I do not have GrimeFighter. Never have.
Upgrade Requests can be disabled, but even so I think I’ve seen 1 in the 5 years I’ve used Avast!