K&N type cone filters do sound the nuts you can't get away from that, unfortunatly they do suck in hot air, which is particularly noticeable in the summer. I ran a Piper x item on my Clio throughout last winter but I whipped it off in the summer as it was noticeably down on power on hot days.
I considered getting a BMC for my current car, but as far as im concerned its just an enlarged factory style air box made of carbon fibre, I doubt it makes much noise being inclosed and is a lot of money. Panel filter and additional CAF if I was going to mess about with it.