Cisco WAN :: 3900 ISR G2 AES256 Support In Hardware?

The datasheets indicate that the 39xx series ISR G2 routers support AES, but they don't indicate if they handle both AES128 and AES256 in hardware.  Via our account manager, we've heard that they only support AES128 in hardware, but not AES256.  Given there's no equivalent of an AIM-VPN/SSL-3 module for a 39xx router, this could be a problem for a deployment we're looking at doing.
 
I can find no document anywhere on cisco.com that confirms that AES256 specifically is supported IN HARDWARE on, say, a 3945E router.
 
And, if it is supported, are there any performance numbers available for throughput?  We're trying to find out if a 3945E is appropriate, or if we need to go with a 7206VXR w/NPE-G2 and VAM2+ module.