We have an extended orchestral version of that theme that plays when Cadance and Shining Armor blow the changelings out of Canterlot, followed by some This Day Aria Super Mario Galaxy crazyness, and finish with a bit of rap about shipping. Check them all out below.
MLP:FiM Love Conquers All (Extended Orchestral Version)
2.) This Day Aria (Super Mario Galaxy Orchestral Remix)
3.) A Shipper's Revenge (The Shipping Rap II)