The "GC8" is a model code from Subaru to distinguish the Impreza RS and Impreza WRX or just Impreza. In Japan, the WRX already existed with the 'prior model design' (GC8)...Unfortunately, it wasn't until the new age Impreza (WRX) came out here...but because in Japan, WRX always existed before it came to the US, the distinguish by codes between the two; thus GC8 - pre 02.
Hope this helps....:nuetron: