There are two ways to connect an additional router:
1. Set the original modem-router into "bridge" mode, to make it work as a dumb modem, not a modem-router. The details depend on your modem-router. Ask Bell for info on this or search the manual if you can find one.
Then connect the new router as a standard router, using its WAN port. Set its Internet options, wireless options, etc., and you've got the solution you originally wanted.
2. Disable the wireless on the old router, and connect the new router to it as an access point. Connect the two routers LAN port to LAN port, and disable the DHCP, uPNP, etc., on the new router. There are some on-line guides for doing this. It's not too hard.
The wireless settings on the two routers should be independent of each other, but it's possible for one to use up some of the available wireless frequencies, so it'd be better to turn off the one's you don't intend to use.
Edit: Hmm, but unless you have already have wireless-n capable clients, you'll need to run the new router in compatibility mode, so will have a wireless-g signal going out. There are conflicting reports about the benefits of running mimo/wireless-n devices with standard g clients. Some claim benefits with just a router change. Perhaps many who promote mimo/wireless-n end up using matching clients.
Sticking with standard g, you could try a Buffalo WHR-HP-G54, which has a built-in wireless amplifier, as a router or access point.