Manufacturers know how to make air boxes, if anything you'll lose power with a cone filter. Go for a K&N or BMC panel filter instead Or depending on your budget you could get a BMC CDA.
I have a K&N panel filter on mine. I don't think the position of a cone filter under the battery would benifit much as it would suck up a lot of stale warm air. The K&N panel filter fitted in a standard air box will work a lot better as it's shielded from all that crappy air under the bonnet plus once fitted you pretty much just leave it alone forever
You`re all right...i think thats the right thing to do....My friends told me to put one in my car because of the sound they also told me about something like thermoshield for the the filter???