PIX Firewall with VPN behind NAT

I'm wanting to put in a dual-wan router connected to two different ISP's to increase reliabilty and throughput of our network.

We currently have a PIX 501 connected to one of the ISP's routers. The PIX has a public IP address on the WAN side. A service provider is connecting to our network using VPN through the PIX.

The Dual Wan router (Hawking H2BR4) has the capabilty of routing all ports from an external address to an internal address. (What they call DMZ) The Pix firewall would phisically have a private address on the WAN side, but the Dual Wan router would send all trafic directed to the public address to the PIX's private address.

Will this keep the VPN from working?

Thanks,

Tim Sanders