performance question

hey everybody, im new to performance upgrades and i got a question. right now my engine and exhaust is completely stock, well except for a K&N air filter. but my question is, if i get a ractive catback exhaust, and a ractive long-ram cold air intake (probably still use the K&N filter?), how much would this boost my horsepower? would it be a pretty noticable difference? thanks for the help.