I have almost the same setup as you on a EF manual.
I am running pacemaker headers, high flow cat, 2 straight through mufflers, 2.5 inch mandrel bent system all mild steel.
Sound wise, you almost can't notice it cruising. It has a burble from about 1500 - 2000rpm but doesn't start to howl until 3000+rpm
Performance wise, don't expect too much if this is the only thing you have done to your car, add a cam and things should start cooking up quite a bit! Mine seems to rev out to higher RPM better, probably due to the better headers.
I had my computer disconnected a couple of weeks after fitting the exhaust when I needed a new starter motor, the car seemed to run much better after this. I say 'seemed' because I did not get the car dynoed before and after the exhaust.
It seems from your post you are only getting one muffler fitted, that could be quite loud - just the way I like it! If there is one thing I do not like about my system, it is that it could be a little louder, but I'm young and stupid, so that me change over time (but probably won't).
Let us know how you go.