i have a couple of options
mazdaspeed
greedy
hks
or custom from mazmark
don't know which one to get

Welp.. it's all up to you.. if you want a big loud exhaust then the greddy's are good... if you want something in the middle then there's the ms.. can't really comment on the hks or a custom job... but with either you'd be going with something that most people don't have.