Panel filter replacements will give a very marginal increase. Their main benefit is that they last forever and can be cleaned. Most air induction systems are routed all around the engine bay so as to provide the engine with the coolest air possible, quiet induction noise and with vehicle packaging in mind. Thing is this means that in most cases for the engine it is like sucking air through a straw - difficult!
If you want breathing improvements then a K&N 57i is the only way forward, the downside of these though is that hotter air is likely to enter the engine. In town/traffic driving this can cause the engine to stall. This isn't the case on all cars though.
I fitted one to my 205 GTi years ago and it made a MASSIVE, and I really do mean MASSIVE difference to the way the car drove. The otiginal system is horrific. It also gave a beautiful induction roar.