Ditch the modem... as for the Linksys or any other router check it's got a modem in- as if it doesn't, you'll need to buy a separate one. (Unlike people on ntl who have the opposite. (We have 1 Mb/s via SACM taken into the Belkin router and it's fine, I'd assume the analog with a modem included works well too)... in terms of specifics I can't remember off the top of my head whether that model does include a modem- check...
The signal will be fine as long as:
- the router is placed centrally to your PCs (ie not tucked away in the corner of the house
- the antenna on the PC is not buried in the wiring at the back and is relatively clear of metallic obstructions (so basically be careful if your PC looks like M6 Junction 6)
- nothing like large water tanks, in-wall metallic obstructions, microwave ovens or 2.4 GHz cordless phones are in the way
- make sure there's the minimum possible number of walls between the router and the PCs- if necessary draw a plan of the house and where you may wanna site your PCs and site the router accordingly
- if you can wall-mount then do so, higher is better (like TV aerials)
- if you can adjust the rotation of the aerials on the router then do so - and set it on mixed-polarisation which means your antenna will get as good a signal if it's oriented up-down or left-right
- better still try and get one with unscrewable aerials then you can get amplifiers, bigger aerials etc etc...
Anyway I'd be seriously going over old ground, there's several info threads on wireless and security etc (which could do with being written into articles
)