i had a borla cat-back on my 03 coupe. sounded great. not too loud at idle but nice when opened up. even had a corvette guy I played tennis with compliment my coupe when I started it up.
on my 07 g35 sport, I went with the stillen exhaust since they had a promotion for the free intake when you purchased it. nice rumble but it had a bit of a drone while driving around. I no longer have either car, but also considered borla for my current 13 lexus gs 350. I settled for a tanabe axel back on the gs 350 since i'm much older now and the borla was made for the model year after (2014 which was identical except for the exhaust pipe routing). hope this helps.