The amp – any pro amp – only uses Speakons for the speaker connections. For inputs the iNuke can take XLR or 1/4”. Your best bet would be to get a RCA to 1/ 4” cable. It doesn’t matter what connector you use for the sub cabinet, but it might be easier to find a speaker cable with Speakons on both ends than one with a banana plug on one end.
Regards,
Wayne A. Pflughaupt