Metrum Hex DAC

The Metrum website for the Hex DAC lists as an option, "extended output transformers" for a price of 168 euros. Does anyone know exactly what this does?
It is a larger core output transformer which has 10dB more headroom over the stock output transformers. The stock units will sound warmer and a bit more romantic with the larger units sounding more real world, dynamic and closer to the sound of the balanced output. Remember the transformers are only for the single ended outputs. Hope that helps.