Welcome to ClubWRX!
NA Subaru's are more reliable only because they have less things that can brake. Namely the turbo charger, these tend to fail after a few 100k. The Maintenance schedules are even the same (well on the 2005's they where).
Older models (01's and older) had hood scoops for looks alone. Even the early 90's turbo legacy's, as they didn't have intercoolers (USDM).
In 2002 the transmission in the RS and WRX was the same, but sense then Subaru has changed the WRX's 5speed transmission almost every year for the better. Not sure if the RS/i has gone though the same regiment.
Why would an intake cause the engine to bog, unless its running too rich?
To make your car louder, just add any Cat-back exhaust. No need to change the entire exhaust if all you want is it to be louder.