Right I've read this post from start to finish about 3 times now and I've come to a conclusion...
wait for it, it's ground breaking...
It's all down to personal preference!
I was going down the route of a BMC CDA but after much consideration I too will be smoothing the airbox, drillig (a few) holes and getting a bigger cold air feed and panel filter.
For the sake of a few hours tinkering and a little pennies spent I can't see this doing any harm in the long run even if it does only give a crisper sound to the induction roar.
Nobody sems to have any scientific or data logged proof that this will increase bhp/torque figures and to the same reasoning nobody has noted any adverse effects so it's all good IMO.
Now to go get the bits for the job!