Hello and welcome to the Fryette Forum! The PS-2A would be an ideal choice since it has both a line output, which gets its signal from your amp’s speaker output, and the ability to attenuate your amp’s speaker volume when running the 4-12 speaker cab. You would most likely want to insert the PS-2A between the Neve RNDI and your Apollo Interface. And you probably don’t need the additional amplifier channel in the LXII. Please let me know if I can assist you in any way. Cheers! Gil https://fryette.com/content/Power_Station_PS2A_Manual.pdf