While DSL is becoming more standardized (down to a 'few' competing specs, for current-generation equipment, enough to allow implementing in one box... but look out, the next generation is already on the horizon), it's still a little 'bulky' to implement; no idea how many chips it actually takes, but there're analog components and other things to worry about, all of which nibble board space.
Whatever your application, it's generally 'safest' to use a separate ethernet bridge ("DSL Modem"), since the costs are generally the same, and support for various aspects of the PCI and USB devices is non-deterministic in many operating systems.
Something like a
Homeportal 1000 (or HW, I guess is their latest modem-integral model) is always cute, but that's a fair bit of engineering, and they have the benefit of dealing directly with the chipset vendors (and Wind River on the software end, apparently), versus a 'normal human' trying to use Linux or BSD ("be happy if it works at all"), or Windows, where any flakiness to 'rare' hardware's drivers may be easily masked-by or blamed-upon the flakiness of the OS itself.
