Yeah brah , go with a ghetto box and KN stock air replacement , very nice result. Ive sold my CT icebox and made it from me stock one and KN filter , even better result coz CT foam filter is a lil crappy despite its bigger free area ))
I have the K&N, and making your own wont necessarily produce more power, if anything it could end up weighing more and reduce it. The K&N is very strong and light weight, and if you get the polished it looks nicer too. Run it in short ram IMO, that's what I do since our TSX already high end power compared to low.