Can I tie 2 wireless routers together?

[zack2004]

Hooking the two routers together assumes they are close to each other (if they are on different ends of the house, running a wire defeats the purpose of a wireless network)
I like the kiss (keep it simple stupid!) rule for networking. Unless you have over 254 nodes on your network you do not need two routers.
300 feet is the maximum range under ideal conditions: no walls, no cielings, no concret. The repeater is what extends the range of your network to overcome these obstacles.
I found that after setting up the router I can walk around the building with my laptop and monitor the signal strength on the wireless nic. When I see the signal start droping below acceptable levels that is where the repeater is needed.
The repeater does not need a computer hooked up to it (except for configuration), so it can be placed anywhere you have a power outlet. You can use more the one repeater per router as long as you give each one a unique ip address that is not in the dhcp scope.
Since you have two cable modems you might consider setting up two indepndent wireless networks, one for you and one for the family. This can be done by changing the internal network address of the second router and giving the network a unique ssid.
Or you can return the second modem and router and get your money back!