I'm not sure why you're confused because REL recommends this type of connection. Is there something unique about your system that would prohibit this? If you have the Neutrik Speakon cable, then the hookup should be straightforward: on the bare wire end, 2 positives (red/yellow) and 1 negative (black) connect to the speaker terminals on your A-S2000 (use the same terminals as your fronts if possible), and then the Speakon end connects into the Hi level Neutrik socket on the sub. This is the MUCH preferred type of connection for 2-channel listening. Here's a link to the R-Series manual if you need it: REL R-305 manual
Yamaha A-S2000 and REL-R305
Help please; I’m still a little confused here; not sure if the high level (speakers) out is permissible to feed my REL R-305 sub. I have two conflicting answers. Thanks.