I currently have a regular magnaflow muffler installed on my car. I would like to know if there would be any gains in putting a cheap ebay twin-loop muffler or should I just stick with mine.

The Magnaflow and the ebay mugen style muffler?

 

I run a full magnaflow catback on mine, and so far of all the exhaust i have heard i like it the most but it just depends on your style adn what kind of setup your running.