I got myself a SS Inductions CAI about 6 months ago off ebay, brand new with the modified bottom of air box for $50 plus $15 for shipping from Adelaide and i've never looked back really. It looks awesome sitting on top of the radiator (look at my other posts i do have pics of under the bonnet) and i have noticed better top end response. Economy wise...well to tell you the truth i never really took notice of economy before i put it on and after soooo lol. I suppose you can't justify the price tag of the SS Inductions CAI that are selling upward of $150 but if you can get one cheap like i did, then get it. As for the s/c CAI, i reckon you would get better than standard top end response also, only because of the force fed cold air at higher speeds into the bigger mouth. I've heard of people opening the mouth up to a bigger size on the s/c CAI as well simply by using a hair dryer or heat gun and opening the lip of it to allow for more air to enter.
Just my 2cents worth,
Cheers,
Boojakz.