I''m assuming it's a HKS Hi Power axle back... Cheapest I found new was $267, but have seen used ones go for at least $250.
http://streetrays.com/store/index.php?target=products&product_id=31502
Sound clip with stock setup with the axle back. Click through for an updated vid with a header added.
<iframe width="420" height="315" src="http://www.youtube.com/embed/CiOPYnqn7oY" frameborder="0" allowfullscreen=""></iframe>