Re: Should I upgrade rear surround speakers.
Before I got my Towers, I was using the HTM200SE for surrounds with S2 across the front. Worked fine. Subsequently, I moved my S2 to surround and the HTMs to my office. Also use HTMs as Heights (F&R). IMO, comes down to your budget and placement options - the HTM & Lunas could be flush mounted to the wall, the S1 & S2EX need some space due to the rear port.
* LG OLED65E6P, BenqHT2050A
* Anthem AVM90, Rogue ST100, VTV Pascal 7 ch
* Sierra Towers/Horizon (all ELX RAAL), S2EXv2 surrounds, HTM200SEx4 heights, Rythmik E15HPx2
* VPI Classic 1+ (VTA & Fatboy Gimbal), PE Eagle/RR, VAS NOVA, Soundsmith Paua, Manley Chinook, Bob's Devices SUT, SugarCube 1 mini
* Oppo 203 & 103D, EverSolo DMP-A6
* miniDSP Flex, Audiosensibility & Blue Jeans cables, Symposium & Isoacoustics, GIK
* For RDJ: Anthem MRX720, Sierra LX, Luna Duo v2 center, CXNv2, TBD