The AC power adapter used with the 5660 is made by EDACPOWER model # EA11203 and it puts out 20V 6.0A to the notebook itself through a 4 pin plug you can see in this picture:www.pctorque.com/46.jpg
Sager does not offer a DC-DC solution YET... I've talked with EDAC myself and the product has been approved and supposed to be available the beginning of December. So, for a little while longer Sager will only offer the DC-AC inverter option that you have to convert back. I doubt you will find anything with the 4 pin plug with those specs currently on the market though I could be wrong.