The module for 6500 load-balancing is the ACE module (Application Control Engine). It runs software of it's own which you can specify when you purchase the module.
The module for firewalling is the FWSM (Firewall Services Module). This also runs software of it's own which you can specify when you purchase. It should be noted that the FWSM is not an equivalent of the ASA ie. the FWSM only does firewalling, it does not do IPS/IDS/content filtering etc.
Both modules have the ability to run contexts which means you can have multiple virtual load-balancers/firewalls on the same module. These contexts are to all intents and purposes separate devices running on the same physical hardware. You can purchase context licenses depending on the number you need.
Wire speed is misleading because the FWSM has no input ports as such eg. a 48 port switch (or module) running 10/100/1000 ethernet could be considered wire speed if the switch fabric for the switch, or the connection to the switch fabric for the module was 48Gbps or more so that all 48 ports could run at full 1Gbps speed and there was no contention. The FWSM has no input ports as such so it's difficult to talk about wire speed.
The FWSM can support up to 5Gbps of throughput but there are standalone ASA models that can support significantly more so in pure throughput terms there are better options available. But there might be better reason to use the FWSM eg. a good use of them in conjunction with the ACE module is to provide mutiple contexts where each context on the ACE module lines up vertically with each context on the FWSM providing you with multiple load-balanced and firewall contexts.
A lot depends on your specific requirements.
Jon
