These drivers work great: http://www.fasttech.com/products/1110706 You can put up to around 30V AC/DC in. 12V in would probably give full output with that array, but 15V would be better.
The PT4115 driver chip on them even has a dimming input that you can connect a pot or PWM signal to. Some discussion of it starting here: Nichia 219 Desk Lamp Retrofit