twins would be hard, there is no ignition for a twin to steal from. You can do this though, you have enough power there to run two HID lights but not two regular ones.
If you don't have a battery in the sled, you will have to run a capacitor to help start them. Once running, they only use 35w each, total of 70, your stock single should be a 65 on high beam.
HID lights are great, you wont want to go back. check out ddm for lights, you need a Dual kit for H4 bulbs with hi/low or you can just run one in your light you have now, Either way, it will be way better than stock. You will want the 4500temp or 5000, no higher or lower. Do a search, also, your windshield will need to be changed as well.