I would personally avoid k&n air filters. Their filtering ability is mediocre (high silicon values in countless used oil analyses), and you always have the possibility of oil coating the MAF sensor. I don't know if its possible on our subies for the oil to coat the maf sensor, but it's been an issue with other car makes.
I tried a number of regular air filters, but experienced poor fit issues with many of them. Click the link below for some pictures I took that illustrate this
The filters like the fram shown above have a slightly curved filter frame that prevents them from sitting flush in the airbox. I understand that you have a 2011 and I have a 2009, but our cars appear to use the same air filter so I think you would experience the same "problems" that I did with various air filters.
I found that the STP air filters fit pretty good, but noted that in many used oil analyses there was a link between above average silicon numbers and stp air filters. Above average silicon means the filter is filtering poorly, or theres a leak in the intake somewhere letting dirt in, I assume #1 based off the number of reports i viewed.
So I recently decided to buy an AEM dryflow air filter. It is a dry, washable filter that appears to have very good filtering ability based off the low silicon numbers in used oil analyses. The rubber gasket also provides an excellent seal in the airbox, unlike the so-so seal I would get with a rigid plastic filter with a felt gasket. For $40, I'm very happy and would highly recommend it. Crummy camera phone picture attached below