from looking at your avatar pic it looks like you actually have a 'short ram intake' or SRI for short 

SRI - (short ram intake) the intake arm and pod are inside the engine bay
SRI is better for higher-end revs but suffers from heat soak, usually has a more barky sound 

CAI - (cold air intake) the intake arm extends down through the engine bay and ends with a pod inside the front guard of the car
CAI is better for all round rev range and retains more low to mid (which is better for the 2.5 anyhow) it also does not get any heatsoak and has a deeper sound

i do beleive there is a chap on here that makes them ...  have a look in the trader section

the RX liberty has a CAI that goes to the front grill of the car standard so effectively u can get away with a drop in filter ... but a proper CAI system would be better, problem is most of the ones around are all custom made, i struggle to find brand name CAI for our model car =/