ImprezaGxDino

Hi all, i'm new to site and new to the world of Subaru's. I have a quickie question about an exhaust im looking to put on mine as i'll be looking to do this Saturday.

I have a 54 plate Impreza GX which is a quiet as anything and would like to actually get some sort of sound from it. Nothing consistently roaring away but more like the traditional Subaru sound. I know I cannot achieve this exactly with a GX due to having equal length headers, etc

A friend of mine has an 04 plate WRX Sti and was given a spare Prodrive exhaust when he bought it, which ive now got my hands on to try out. My questions are, as im sure you can all guess by now is....
1) will this fit? just a visual check, my original and the prodrive one seem very similar but very hard to tell exactly whist one on and the other off
2) will it work? i.e performance issues, back pressure issues, etc

Thanks in advance