I wouldn't recommend using MIPS or VIPS in a hosting environment. NAT is good for corporate stuff or LANs. I know CPanel doesn't suggest running servers with NAT. I usually get a /30 from my ISP for the "untrust" side of the firwall. The your public IP space (however many IPs you need) would then be set as the "trust" side. Put a static route between your trust to untrust side and you're done. I use Juniper firewalls, but I know Sonicwalls and every other decent firewall on the planet can do this.