Best dual WAN load balancing + failover site to site VPN firewall?

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http://hardforum.com – Hey everyone, I have a customer with two offices, one in Chicago and the other in New York, and each one has dual WAN connections currently. Their current firewalls in use can only do site to site VPN with dual WANs in failover mode, not load balancing. We are looking to implement a new firewall VPN router at each site to be able to aggregate these dual WAN lines (about 50Mbps and 70Mbps connections on each end) to combine the bandwidth into one massive site to site VPN link. If one WAN goes down, the line just downsizes seamlessly onto one WAN link with no interference. The only prod (Hardware)