Though this air filter thing is an endless debate, I still tell my opinion. I have Pipercross cone filter which should be good. Atleast certain engine mapping specialist told me that it is one of the best air filters you can get. It was in my car when I bought it so I let it stay, it also makes awesome induction noise.

However if I would have the original box in the car I would put K&N panel in it and drill some holes in the box to increase airflow, and perhaps some kind of induction pipe. Airbox protects the filter better from heat of the turbo (should not be an issue, atleast in high speeds because of airflow), but cone filter should have bigger surface area.

Either way, I think that any aftermarket filter, whether it is cone or panel, will do the job. Difference beetween them is at best probably couple bhp which has very little meaning in turbocharged car where you can gain more hp with other modifications...