Just for reference, the Rythmik Audio HX300 servo amp has been discontinued.
The HX310 is the replacement being built for production. No time frame has been posted.
For the 4x8in servo sub towers I took to CAF 2023 with the Magnepan MG10/QR's, it was a pair of original HX300-8OB servo amps I had on loan from Brian. Now run them with A370XLR3's with the dspNexus 2x8 with some EQ to replicate the HX300-8OB operation.