Hi Jim
Policy routing or policy nat should help you do this. You will be able to do destination NAT based on the source address by attaching a route-map to your nat statement.
Or you could you the policy routing to set the next hop based on source address if the servers live in different subnets.
Or a combination of the 2.
Here is a link for policy routing
hxxp://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009481d.shtml
Let me know if you need any more help.