Cable companies might still ship modems (they did the last time I had cable internet, but that was probably 8 years ago).
Amusingly, they always set the SSID to 'insight_wifi_XXXX' and their formula for WPA keys is `firstname[0] + lastname + housenumber`.
That coupled with a router/wireless ap running tomato or the like should work well from what I understand. I, however, never have used DSL so I'm not an expert.
There's nothing to return, I get DD-WRT instead of whatever garbage they're running, and usually measurably faster in both internet speed (usually lower latency) and wifi speed. In particular, I've never had a bundled device get within 50% of what 802.11n is capable of, especially when you have 4 or more devices. All my dedicated routers have done just fine.