Which GReddy???

Well, I finally have my GReddy exhaust ordered. Currently its the GReddy Street Performance exhaust, but the shop told me that I can get the EVO for the same price. BUT, I might have to wait a bit lnger for the EVO. What do you guys think? Should I wait for the EVO or get the SP now? If there's a chance to get the EVO now should I get it.
What do you guys know about the two exhausts, as far as sound and performance. Any feedback will be appreciated, as my appointment for the SP is three days from now.