40 hp is no easy feat when keeping to a daily driven naturaly aspirated engine. Complete header, catback, intake system will get yu to the most 10 hp with the new k series engines.
Unfortunately, your new rsx is still waiting for the aftermarket world to produce more power option.
fi-->forced induction-->turbo, superchargers and Nitrous kits
This would most likely be your best bet, a properly tuned Nitrous Oxide Kit.