I had a GSR before which had the type-r cat back and i got this muffler on ebay for $150 shipped (shipping cost the guy about $25) that i was going to install before my car got stolen. I also heard a lot of people complain that the Apexi was loud. But my brother had it on his 240SX which is a DOHC 2.4L engine and it sounded awesome (not too loud at all).
So i finally replace my GSR with the Lude and it had a custom Meineke cat back installed (probably replace that soon too). I went ahead and just had the Apexi N1 turbo muffler installed and it sounds great. I think that these huge free flowing muffler/exhaust sounds better on bigger engines. Can't get a sound clip right now but i'll post it as soon as i do.
And yes, i think i'm going turbo soon... but i have to move out of my cheesy apartment complex which i believe houses thieves.
I also got a silencer but it was for a NA muffler so i didn't get a chance to try it out.