Re: Pair Original Sierra-1s with which Atmos/Surround speakers
Personally, I'd steer clear of any of those "up-firing" ATMOS speakers. When I was researching ATMOS for my upgrade, that method was a distant third. First was on/in-ceiling, 2nd was high on-wall (about 90-95% of on/in-ceiling), and upfiring bringing up the rear. Due to my room, I went high on-wall (front and rear).
Personally, I'd go with either the LX or EX for LCR. Maybe leaning towards the LX for HT although I do love the RAAL tweeter. Or, keep the S1's, depending on your budget.
Further, I'd look at the HTM200s or CBM170's for surrounds, particularly if keeping Sierras up front. For ATMOS, depends on where you are placing them. The HTM200's work really well for ATMOS duty (and surrounds - I use them for ATMOS and used to have a pair as surrounds).
* 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