All down to preference mate. A Hill Power kit will cost about £250 and I don't think that includes the Bend which would be advised, maybe even required. The BMC is about £160 I believe and again would probably require a silicone hose. Then there is the ITG Maxogen or the PiperX Viper, all much the same as before and muchos dineros £200+.
I have a standard box with PiperX panel, 70mm air feed running to the wheel arch and a silicone inlet elbow. Total cost £40. I did get a couple of the bits cheap/free but it should cost no more than £60 and a bit of time.
I can't see a Viper etc doing the job any better.
I even asked Andy at GDI wether a sealed IK would be better and the answer he gave was that my current setup would be more than adequate.
Good value as well and satisfying knowing you have done it yourself.