I have bought a CB400F muffler from David Silver spares and the quality was very good both in build and weight of the item and the chrome finish. I believe they are made by a British factory for a number of the reproduction exhaust items that they sell.
They have a reproduction early model Goldwing muffler at a cool $1850.00 US for that set up, so you are talking large amounts of money here even at $1200 for your set. I would expect the quality to be top notch and I feel David Silver spares lives up to that objective on any reproduction parts I have bought in the past.