Milltek are good for the FN2 and reasonably priced.
Most systems are quite expensive though, you're talking near a grand for HKS, over a grand for Toda, Mugen, Js Racing or Spoon.
Tegiwa do a single exit like the Spoon, that's reasonably priced.
Steer clear of Blueflame, not great quality. Last year Blueflame bought the Magnex name and started shipping Blueflame exhausts rebranded as Magnex. Nothing like the original Magnex quality so be wary about later Magnex exhausts.