I went through the same investigation about a year ago. Just when I was ready to take the plunge, my local telco called and said the DSL was ready, did I still want it?
The upshot is this.
If you get a stand alone unit, you can usually find a rj-45 connector inside (take the back cover off the box, voiding the warrenty and making the service tech nervous) to plug it into the back of your SME box, after you configure it with a windows box.
Configure with the windows box and the provided software. Disconnect from the windows box. Open the unit and there should be a rj-45 connector with a short pigtail going to a connector on the back panel. Unplug the pigtail and plug in your cat5 to the unit and to the SME box. You should be good to go.
If you get a card (sometimes 2 cards). you'll have to dedicate a low budget windows box as the interface. Put a nic in it and connect it to your SME box like a modem.
All in all, it's the worst of all possible choices for broad band, with the exception of no broadband. Ping times in the 3-5 second range (or longer, so on-line gaming is painful), regular drop-outs and weather related problems.
Good luck.............