My car arrived into my care with K&N "pancake" filters.
The engine was freshly rebuilt... and it died a miserable death about 10,000 miles later. I do NOT attribute its death to the filters, but I resolved to revert the car as much to stock as possible. It took me forever and way too much money to acquire the stock filter assembly on ebay. I was within a few weeks and a couple of stray parts to having it restored and back on the car when I was notified by SNG that I had won a photo contest of theirs! The prize was a parts voucher. The value of the voucher matched the cost of their ITG "performance" filter, so I figured "what the hell!"
http://chuck.forest.net/jag/KnNremoval/
The first thing I noted was that the car's torque curve no longer flattened out in the midrange. That was a surprise. The K&N's are *supposed* to be a performance filter, but in reality they hindered performance. Go figure.
So based on that, I'd stick wit your stock setup, or something that emulates it like the ITG one.
The K&N's looked cool, but they were basically worthless in my opinion.