an enclosed kit is better simply because it only get cool air from outside.
K+N has a pipe which blows air onto the kit, only onto a small portion mind, but it is also exposed to the warm engne bay air/temperatures.
A kit like BMC, most likely you'll need to get one of the universal ones. DO NOT GET BMC ITSELF - TRIED AND TESTED IT IS TOO LARGE. IF YOU WANT TO MOVE THA BATTER THEN YES YOU CAN GET IT TO FIT.
Hothot on the other hand is a CAI and has a different approach.
The filter is places under the car, behind the passenger fog lamp and air from outside hits the filter directly. This then travels up chrome piping which comes from the engine bay. This is probably the best system as the filter gets the most air, but also gets only cold air from outside
About the best explanation i can give
HOWEVER.....................
A new panel filer, K+N for example into your current air box and a custom pipe would be like an enclosed kit, i know a few people who have done that and don't give a toos how it looks. Looks wise its not as good as your fancy carbon enclosed kit but it works on the same principle
Again you can have a kit like hotshot welded for you - got to know the right people etc
HOPE THIS HELPS ALL 1.5/1.8 N16 ALMERA OWNERS