Geographic Server Load Balancing

The company I work for has two main sites, one in Hawaii, the other in Chile.

We currently are hosting out of our Hawaii site. Because of the long distance, users in Chile have never been happy with server response time. We are planning on upgrading our sun hardware to opteron or niagara. We want to reuse the older hardware with the new stuff in conjuction with a load-balancer.

Anyone have experience with geographic server load balancing from Foundy, Coyote Point, F5, Radware? I've only had discussions with foundry on their product. As we currently use Zeus in place of Apache, we did look at Zeus' offering, but it was priced well out of our budget (like cisco) and offered no geographic load balancing features.

Redirecting traffic to the appropriate site based on response time makes a lot of sense and will make our Chilean users happy.