Hi Matt,
Sorry about the delay. I have worked on similar projects, and JEE/JMS works well for this sort of thing. Another technology you might consider is Akka, which could easily help you implement the message distribution. JEE is a good candidate for this sort of project if you also need things like persistence, web capabilities, JNDI, etc. Obviously, most JEE containers implement clustering and failover, too, which is a big mark in their favor. For very high message volumes, you always need to get creative with caching, load-balancing, batching, etc., but in my experience, JEE scales very well out of the box (to, depending on the task and configuration, 10s to 100s of thousands of operations/second)
Best!
Josiah