I bought a CAI for 56.00 on ebay. Not ONE company has real data that their product performs ANY better than mine - 
I put the K&N drop in in my S/E and saw no improvement to performance or MPG (over 2 months).CAI at the most will gain 1-3 ponies. The best is probably the cheapest. Throw in a k&n drop in filter and leave your box alone for the best hp gain. If you are going for looks and bling (Mike I know you are), get what looks best as there is no real performance difference.