|I agree with guapo 100%|
Moving routing from a router to a server is not logical. Moving it from a router to a DC is just silly!
Sorry, I don't mean to be rude but, when it comes to DC's, you should be offloading any/all services you can off of them. For instance, you're running websites on your DC. If it were me, and I had 5 other servers kicking around, the ONLY thing the DC would be doing, is acting as a domain controller and running DNS.
I would move DHCP and IIS (and all web pages) off of it and on to a member server.
All websites should be on the same server running IIS. All incoming port 80 traffic should be sent to this machine. Then IIS can take care of directing which traffic goes to which web site.
I'm curious, since you have 5 spare servers kicking around, do you have a second, redundant DC ready to take over should your first DC fail? If not, you should do that too.