Connecting Velodyne F-1200 Subwoofer

Hi - we have a Stellar GainCell preamp and S300 power amp. Normally, we have a REL T/5i subwoofer connected and it works great.

We also have a (very old, but still works) Velodyne F-1200 subwoofer that has a set of speaker-level inputs (positive and negative terminals). I always used those when connecting the Velodyne to our old system (non Class D amp), connecting directly from the power amp speaker terminals to the Velodyne speaker terminals. Does anybody know if we can go from the second set of speaker terminals on the S300 directly to the speaker terminal inputs on the Velodyne?

If using the speaker-level inputs doesn’t work, the Velodyne also has line-level stereo inputs. If we are using the balanced interconnects between the pre and power amp, does anybody know if we could also use the RCA outputs from the preamp to the subwoofer.

Thank you,