The only difference between the powertec sl1 kit and the k&n is that the powertec is stainless steel and the k&n is cotton gauze. the steel offers better airflow but the cotton apparantly filters slightly better.
personally I ditched my powertec because i wanted to go enclosed in the form of my bmc kit.
Of the 2 I would go Powertek because it look s so much nicer and its lower maintainance (i.e. no oiling needed) and it has better airflow

P.S. Fordie, you dont need anything extra to fit the powertec other than a screwdriver. All is provided for your convienience. And get it from ESP design it s cheaper than anywhere else I think.
Aaron