A couple of other things you can experiment with on the audiophile mos125 and mos250. The 2.2kohm resistors feeding the shunt regulators for the opamp can be replaced with a constant current source, something around 15mA should be fine. This will greatly increase the power supply rejection. The shunt regulators can also be improved if you bypass the resistor feeding the adj terminal with a 22uF capacitor. Its also possible to improve on the constant current sources loading the opamp by using a transistor/transistor rather than a led/transistor source. I haven't tried any of these suggestions yet but if anyone is interested I can provide more detail.
