You dont need to load balance speech server to scale out for an outbound dialer it uses MSMQ.
You could have your application send OutBound call requests to multiple MSMQ's on Multiple speech server like a round robin scenerio. Speech Server outbound dialers are tied to Microsoft Message Queues.
Also for large outbound applications I would recommend using a Ingate SIParator to use a SIP Trunk with Speech Server. I have used it to place 50,000 out bound calls. I only use 5 Sip trunks to complete this and its free long distance.
If you want more info send me a request from my blog site http://www.ocsmvp.com
you could use an F5 load balancer to use one host name or IP address that could be using multiple speech servers behind the device. If you buy a Quad core server you can place 96 outbound calls at one time and the server will manage this just fine.
Keith Kabza MVP