Those ebay cores are shit… they will flow the volume of air needed for x hp but will not cool it as well as a similiar garrett.
PTE intercoolers are cheap and with cast end tanks and garrett cores, you want both things. The core kevin used was good for 750whp and are decently priced at about $450.00
Since hybrid is not taking orders at the moment here is a link to mikes store… http://www.innovativetuning.com/catalog/product_info.php?cPath=486&products_id=2778