Digital in for US-428

[dlbeaty]

Seeing that my US-428 is approaching 20 years old, I am preparing for it's demise. So far I find no interface that supplies both MIDI control, 2 MIDI ins and outs, 4 simultaneous inputs and is designed primarily to be used for DAW recording. I am curious if an upgrade to a preamp with high end D/A converters digital out would give better results for now and in the future. However I am confused about issues like wordclock and synchronization, since this model has the RCA in and out only. No wordclock connection. Any sources out there to recommend me for information?