Desparate! Which middletier?

HI - I've been researching intensively over the last month wrt which middletier to use in scaling up our IVR system and I still can't choose between sockets, remoting, Message Queueing or EnterpriseServices. Being a small company we can't afford an architect so I was hoping someone could point me in the right direction. We're scaling up an IVR system to handle 100's of calls per minute. The system redirects the call to the right operator. Potentially we will have 1000's of operators with basic info stored on SQLServer. Users add/change details. Needs to handle up to 100's of users at once. We would like a GUI that represents in realtime the calls on each port (name of the service, time on line etc) and allows users to enter/change operator details in batch. We will be running a clustered server, all on LAN (no web yet). The current system works with simple sockets but the complexity involved in staying with sockets scaling up scares me, but being a real-time system I'm not sure we can afford the performance hit using remoting, MSMQ or EnterpriseServices. I've been researching Remoting but we will need to use a great deal of events and callbacks. Does anyone have any suggestions as to which way to go and why? Thanks in advance