FYI: The range of the router also depends on the other end. If you have a crappy wi-fi card on the other end, it won't matter what router you get.
I have the WAG160N which also an ADSL modem, but there is the WRT model w/o the modem. It works pretty well. You need to check how many walls the signal will encounter (line-of-sight between the router and your pc/laptop/etc). You will definitely get reception through one wall, but not through two. If you can connect an external antenna to your wi-fi card then you will get decent reception through two walls.
If you need a really long range setup, you will need an additional repeater type device. If you have an old router lying around check if you can flash something like dd-wrt on it. (it even works with access points like WAP54G) You can re-purpose it as a repeater.
