If your going to have 2 routers on the same network, yes, however be aware that this will cause connection issues and double NAT problems. I've heard and it's preferred that the modem be bridged if possible. Also if this can't be done, there is a DMZ if the ISP modem is it that you could put the 825 routers IP address into thus effectively bypassing any processing of the ISP modem. However this still can present double NAT issues.
Might ask the ISP if the modem can be bridged to the router.