If you are looking for spot/floods you can use 110v incandescent, LED, etc. with an LE (Lynx Express) controller.
If you are going with 12v MR16, you can create floods out of 12v parts... there are products for sale, like rainbows. In my case, I took a $5 home depot halogen work light, tossed asside it's guts, and replaced them with 10 5050 RGB nodes (30 color changing LEDs altogether). With this you can use a MR16 with 3 of its 16 channels to control this... but you can choose any color throughout your song. Cost for the nodes... about $5 more.
And another choice -- and my favorite for brightness is the AetherII. This DOES use 12V AC, and it provides a powerful RGB light. When the coops open for this, I plan to get a few more.