The avast 5 antivirus with Comodo without the antivirus will work.
The avast 5 suite (antivirus + firewall) can’t be installed with Comodo, as, at least the firewall part will conflict.
I’ll stay with Comodo with AV off. I like D+ as it tells me what things are trying to do - some installations try to start with Windows, connect to the internet, put files in unusual or irrelevant places etc.
The combination seems to work well; I’ve been using it for about a year now.