I would like to upgrade the exhaust system on my si. I am new to the import world and would appreciate some guidance on what system to install. I am looking at a system from magnaflow, but was wondering if there are any others that are better sounding and performing in the $400-500 range...

there are many exhaust systems out there: greddy, apexi, skunk2. just to name a few. im not sure which pushes put the most HP though. you're gonna have to do some research. or some of the ladies and gents here will help you further. or both : D