Best practices in mixining Actors with traditional Classes

Actors are good at programming multithreading and asynchronous tasks, but there are a lot of scenarios when we don't need them, and it's just an overhead vs method invoke.

Sample

case class ConnectionToServer(
tcpConnection: ActorRef,
protocolVersion: Int,
address: String,
startedAt: DateTime,
user: User
)

I could put all "constants" in tcpConnection add messages to get them.

Can you point me to patterns and best practices how to mix together actors with traditional OOP approaches.