I would say get the rapid cooler system, the airbox is a bit expensive but if you can live with the underbattery airfilter system you can save a bit of money. plazmaman, a site sponsor here has a battery and airfilter kit that will work with the rapid cooler and plenum and mount the filter under the bonnet. im using the same unberbattery airfilter as the rapid systems one and I find it to be awsome, good noise on spool up and proven airflow rates to produce plenty of hp. with the rapid cooler, ub intake siemens injectors and a good zorst and tune you will see 300rwkw without the plenum.