said by clock:
You wont have to contact RCN to change your router. All you'll have to do is power cycle the modem once you connect the new router and you're all set.
Probably won't require a power cycle either, but to be safe you should.
I know this because I've changed devices left and right in trying to get my SB6121 to work. And once connected, it generally assigns a new DHCP address if you switch out the connected router/PC, etc.
BTW: Great choice on the router. Hope it works out well for you.
"Look at me, I'm Dr. Zoidberg, homeowner."