When you say "more powerful" as far as HP, I'm with Cronic...you don't really need name brand, just make sure

1) it's the right size piping for your exhaust & engine
2) no crazy turns in the piping...nice and even flow with Mandrel bents when needed
3) decent muffler/exhaust

If "more powerful" means loudness...disconnect the mid-pipe from the exhaust....you'll hear powerfull