The DP88 was not exclusive to the Quantum series, you can use any ADAT preamp on the market that have been made in the last 20 years new or used. If you want to use an interface, you have to make sure that it can operate stand-alone as a pre-amp. Check with the hardware manufacturer to check device capabilities before investing.
You could use the Apollo Twin if you are sending audio from another computer, just make sure that the two devices are clocked together, one is ADAT Master, while the other is ADAT slave.