Hello Brent,
have a look at the following link about scalability
http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/DMVPN_3.html
Possible design options are to recommend a series of stacked Cisco 7200VXR platforms. At least four are required to aggregate 1000 tunnels; however, this does not provide the needed aggregate bandwidth of at least 628 Mbps.
DMVPN looks like more heavy on resources
Hope to help
Giuseppe