There are many methods to implement a volume control on audio system:
normal potentiometers with good quality like the ALPS It is very cheap but with some limits on noise and precision so this is not suggested in true hi-end systems.
PGA2310 high-performance, stereo audio volume control chip Used in many audiophile components based on op-amp design, not suggested in hi-end audio with no feedback and vaccum tubes
stepper attenuator like the DACT As you know I love DACT because these have really none negative effects on the sound but these are difficult to control remotely, about the quality see the testimonials.
integrated DAC volume control The integrated DAC volume control like in the ES9018 chip is very good if compared to normal digital control implemented by the operating system (this lost resolution) but a good stepper attenuator is much better (see ESS article)
Shunt volume It is the newest trend in volume control, it reduce the components in the signal path so it promises better performances, near or better than DACT if high quality resistors are used.
There are many good articles about this attenuator like the Logarithmic resistor ladder and Logarithmic Attenuator Calculator. Two encoders near the display allow to select the input and to change the volume level. A good infrared remote command is included and it add lcd backlight switch off, mute button and standby function (necessary a second transformer). It can easily integrated the same chassie of your custom pre-ampl. or integrated amplifier. The firmware has been design with standby configuration, so one little 6-7VAC 50W transformer always powered for the controller module and another bigger transformer for your pre-ampl or integrated amplifier. I can modify the firmware on your request to have no stadnby configuration.
Quanghao sell this complete module assembled including the aluminium remote at 250$ + shipping.