uh...Greddy EVOs are actually pretty loud, never heard the Greddy SP myself so i can't give you my input...but if you want a nice throaty/quiet exhaust...get the APEX'i WS. It looks stock, conservative, gives you HP gains, and pretty quiet at highway speeds.

My Greddy EVO is pretty loud, esp. during cold weather. I get nervous on what my dad might say whenever i have to drive him somewhere for some reason.