It is ridiculous to even say there is a slight difference. There is not a human being alive who could hear any difference between these DACs.
I myself listened to and compared both the X16 and the A18 about one ago, together with other current DACs up to € 1000,-.
The differences were definitely there, but we're not talking about worlds, but nuances. At that time, the € 200 surcharge for the A18 was definitely worth it to me.
But you also have to say very clearly that the X16 (then €425) and the Sabaj D5 (then €400) are unbeatable in terms of value for money and that you dig much deeper into your pocket for a little more got to.
I don't believe in any difference,
I think if there was, it would be in favor of the X16 for being a dual chip.
Please do not confuse the number of chips with the implemented technology and performance.
The ES9068A is a 2-channel DAC chip and is traded as the successor to the ES9038Q2M with MQA extension. It also costs only about 1/5 of the ES9038PRO.
The 8-channel ES9038PRO continues to be the flagship in the ESS range, with impressive performances in all areas.
This performance is even better in stereo mode (4 channels are combined into one channel) and as a mono chip it is even better.
But that alone shows what a great performance Gustard has delivered with the X16.