If it is a 45 tooth, then that should be great for street riding; 17/45 should move you along swiftly. Then again, are you trying to improve street speeds? Then again, once more
why would you buy a Magician over a Hawk if you wanted it to be more of a dual-sport? I would use it as is (after buying a new chain) and see how the combo works for you. My guess is you won't need or want a new rear.