On install, any AV software product should look to Windows Firewall rules and try to replicate what has already been allowed - Avast is not great at this.
As one would suspect, its impossible to keep up with all the changes, settings, operations any other software has if there is a conflict with one of our products. Its far more effective for us to point to products (in this case, an AV product) that we know plays nice with ours.
As you mentioned, Kap works well - as does AVG.
