I think you'd be better off with a straight through muffler than a chambered. Would probably sound better too. I think the chambered designs like the h-pipe better...at least that's my experience. I'd give yours a 7...But that's just my opinion, just matters what you like.
i would say at best a 7....probably a 6. i dont like the sound of xpipes on our cars. not saying they dont sound good by any means but i just dont like them. i got what i have in my sig but hopefully by the end of this weekend, ill be doing longtubes with an o/r hpipe