did any of you read his question?!!?!?!? He wants to quiet it down WITHOUT REPLACING his exhaust!!!! Good lord.
The silencer would be the way. If you have any pictures that you could post of your exhaust that would be helpful.

 

Well A) he doesn't know what kind it is B) he doesn't know the quality of the exhaust, so it could rott out in a month, it could last a year, and the silencer would only quiet it down so much for all we know it could still be insanely loud with just a silencer. then he would just be back at square 1. and if he was to put in a resonator for the cost of getting one and having it installed by a shop he may as well just pay an extra $50-100 and get a completely new catback that he knows is quiet

 

Okay the only reason that the silencer wouldn't work is if he had holes in his exhaust. I asked for pictures to see the exhaust.

My advice is on the assumption that his exhaust is a cheapo aftermarket exhaust without holes, that is loud because of the fat can on the back. If his exhaust is stainless, which it seems like most exhausts are now-a-days, then he won't have to worry about rust holes. Thus, the silencer would quiet the exhaust.