There is confusion here on the term ROUTER.
Which you have just added to.
A router is a very generic term for a device that contains an ADSL modem, a firewall (usually providing routing and NAT), a network switch, and possibly a wireless access point too.
NO NO NO
A router is a device that routes traffic between two or more IP networks. It may or may not offer other functionality on top of that. What other functionality it offers will depend on the market segment it is targetted at.
Routers targetted at home and small buisness users will have things like NAT, a built in ethernet switch on the LAN side, a built-in DHCP server, software that assumes a simple setup with "WAN" on one side and "LAN" on the other with very few routing table entries and possiblly a wireless access points and/or ADSL modem.
Routers targetted at the core of large networks will have features like large routing tables, many indepdent ports (not just a handful of ports on an integrated switch) and route learning protocols.
But all of this is getting offtopic, the key point is you can't put more than one ADSL modem (which may or may not be integrated in a router) on one phone line and adding more routers (in whatever configuration) is highly unlikely to help you.
To the original poster, you need to find out WHY your service is slow. The first thing to do is to log into the router and check the "sync" speeds. These are the speeds between your router and the first device at your ISP.
If it's extremely low then you might try complainting to your ISP but their options are limited, ADSL is "a best-effort" service and if the line is just **** there isn't much they can do about it. Moving to a "fiber" (really fiber to the cabinet) package will likely result in much higher sync speeds if it's available in your area but will obviously cost more.
Next you should try using some speed test sites. If they give a much lower result then your sync speed there is probablly a congestion issue in your area. Moving to another ISP may or may not help depending on whether your area is LLU or not and how congested the different networks are.
You say it's slow even on wired when the kids start using their kit. That suggests that the problem is not limited wireless bandwidth.
You should check what your kids have running on their machines. Bittorrent can seriously cripple an internet connection because it's use of multiple TCP connections makes it very agressive in taking bandwidth. A traffic-shaping router may help but you will need someone who knows how to set it up properly. Also virus checks are strongly reccomended.
