EBS2008 – Network Topologies

I am in the process of planning deployment of EBS2008 for a client.

Microsoft are fairly pushy at you making the default gateway for your main Network the EBS security server.

I have a watchguard box as my primary firewall where my branch office VPNs will termintate. The EBS security server will sit behind that.

I also have a leased line to our secondary main site. The traffic for this subnet is routed by a Cisco on the leased line.

Is there anything to stop me using the cisco as the default gateway with appropriate routes or should I use the EBS Sec server and have the cisco sat between the sec server and the watchguard?

Any thoughts on this would be greatly appreciated.