Raymundo,
The 2611XM is EoL.
I believe you don't need the AIM card as long as the IOS supports encryption to terminate VPN tunnels (the AIM is to improve the router's capacity in handling VPNs)... not sure about this though.
If you have access to the router itself, check the ''sh ver'' to see if it has a k8/k9 image and if it takes the ''crypto'' commands.
Federico.