On my 05 600, when I switched to a K&N I lost a noticeable amount of midrange. I might have gained 1/2 hp at the very top, but I couldn't feel any difference up there. I had about 8,000 miles on it when I made the switch, so I knew what it was supposed to feel like. I ordered a stock filter three days later and got my midrange back.
There are other aftermakret filters which may work better, but for me, a stock filter was best.