Can I get document on VIP cards which lists basic difference between VIP2, VIP6-80 etc..?
This link might be of some assistance.
Increased Performance of VIP
The VIP6-80 Services Accelerator for the Cisco 7500 Series Router enables high-performance switching and scalable LAN/WAN intelligent network services to meet the needs of high-performance applications. The VIP6-80 provides up to a 40 percent improvement over the VIP4 and a more than 100 percent improvement over the VIP2-50 when distributed features and quality-of-service (QoS) are enabled on an interface.