AEM is pretty good, Nismo intake is actually a rebadged AEM! If you do fit that and keep it long you will need to remove the 2nd windscreen washer tank... You can run them as a short ram but you will need a heat sheild and they done come with one... My preference is the typhoon but keep the heat shield on!!
As Martin say Nismo is about £1200, cat remember if that is ypipe or cat back, plenty of other options out there like the 5zigen for the same money... Give Envy a call (Gaz Walker or Chilli Red on here!) as they can help...