Speed Concern and Question about Source

I have a two way replication between to identical Databases: C: -> D: and D: -> C:. The replication is very slow compared to IBPhoenix IBReplicator. I have tried multiple threaded and non-multithreaded with the same result. How can I get greater speed out of your product ? Also, if we by the enterprise edition, do we get all the source to the Server and Manager? Regards, John