Moving up in the REL line of subwoofers

All very interesting information. Thanks so much.

To those of you trying to help the OP get the best sound with what he has, I’m not sure you’re understanding the ‘itis’…. 

Move the subs from front stage to the back wall...or along the sidewalls behind the seat. The 2 subs sitting up front (for your viewing pleasure) didn't do some worthwhile things for your room, perception of deep soundstage, envelopment, etc

Lack of long sub cables would be a reason for subpgraditis

I’m not sure you’re understanding the ‘itis’…

???? Please elaborate.

@ronkent Have had several series of REL subs including a stereo pair of 212's.  If you're looking for a great dual-purpose sub for 2-channel and HT, IMO this the best offering by REL.  I had SE models, there are aesthetic differences with the SX but I didn't find a material difference in performance between the two.  Also, may not be important to you but the wireless transmitter option for both allows for really convenient placement without a loss in performance.  As noted, there looks to be a number of either model available used at reasonable pricing.