I think you can safely say, you WONT get mistaken for an ENZO
Why do you think that it would negatively affect performance ? It might just be a raspy exhaust note which isn't a bad thing. You should hear my Rallye dude, it's loud as and I love it.
ive got the same exhaust without the mid box and makes a low burble noise when not caning it, but when you open it up it sounds very meaty, not chavvy or jap noise at all, just about right in my oppinion!!
its actually very easy to fit, just make sure where it goes onto the downpipe is very tight as they tend to slip and it puts the backbox out of line. im sure you'll be very happy with it, and if your feeling extra naughty a K&N panel filter is a good addition!