You will be able to use the Line in inputs on the sub. Just connect the 'Subwoofer' output from your receiver via a digital coax wire to any one of the inputs in Line In. Or get a Y-adapter and use both Line in inputs.
Usually running a sub cable from the avr to the L input will work. So, no big problem!
Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus 200 Five, Dayton 18 Ultimxa Dual Sub Cab(2), Dayton 18 Ultimax Large Vented Sub Cab (2), on Berhinger I Nuke DPS amps, Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
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.