Can I implement Server Load Balancing on a 6509? Or is there something similar I can look into? Any help would be greatly appreciated.
Yes you can. See attached link for details of IOS SLB on 6500 and which supervisors/versions of code are needed.
The other way of load balancing on the 6500 is to use a dedicated load balancing module which uses one of the slots. These being
CSM - Content Switch Module
CSM-S - Content Switch Module with SSL daughtercard
ACE - Application Control Engine
The ACE module is the latest module for load-balancing on the 6500.