I'm assuming you're using the IPSEC functionality of your RVS4000 router for terminating VPN connections (either user-to-site or site-to-site). I tend to feel more comfortable terminating VPN connections with a dedicated hardware device or dedicated server computer, when I can, versus using a general-purpose server computer.
If your Windows Server 2008 R2 machine is also being used as a file server, application server, Active Directory Domain Controller, etc, then I'd be hard-pressed to recommend using it to terminate an IPSEC VPN as well. (Yes, yes-- for years Microsoft's Small Business Server products have terminated PPTP / L2TP VPNs on a server computer that performs every function possible. That doesn't mean it's a great idea.)
If you elect to terminate a VPN on a general purpose server computer be aware that the server computer's attack surface may be larger (because you will need to expose it to IKE and IPSEC-encrypted/authenticated packets coming in from the Internet) than if you'd just left VPN termination up to a dedicated device or server.