In general, a pre-amp, by nature is a 2-channel ANALOG device. To have a digital input, it would be a combo unit, ie pre-amp/DAC or a multi-channel preamp/processor. There are plenty of pre/pros out there and there are some good combo pre-amp/DACs. For 2-channel pre-amp/DACs that would have both analog inputs and Digital inputs, there is a Musical Fidelity unit and there is the Monarchy Model 33 and I'm sure there are others.
Personally, I did own the Monarchy previously and it was pretty good. But, I prefer the flexibility of using a pre-amp and adding an external DAC to take care of my digital duties. There are some good DACs available for under $500 used.
If you insist on having the pre-amp and digital processing in one box and it is for 2-channel music only, the Monarchy Model 33 is a nice unit and cost under $500 used.
Enjoy,
TIC