Nuke

You won't void your warranty with a CAI & tune combo. The tune is about 80% of the combo's power adder. But the combo is a tough act to follow for RWHP addition. Best to get the combo rather than piece-meal since it'll cost you more with the latter for having to buy updated tunes for the CAI.

IMO, the K&N is not the favorite but those that require a tune all perform about the same. Buy based on what suits your eyes and wallet.