The receivers you are looking into don't have an L+R sub output. They have 2 LFE outputs, meaning you can hook up 2 subs. A Y splitter will do or following your sub manual direction for hooking up the LFE cable (I think it is the left input in your sub.) I think the subs have L+R to be use on different kinds of preamps and not in AV Receivers, but I'm not really sure.
Yamaha RX-V673 | HSU HC-1 MK2 | HSU HB-1 MK2 - LR | Pioneer SP-BS22-SLR | BIC RtR-V44-2 (Presence)