Speaking of diminishing returns...
I decided to try out the Sierra 2s as rears the other night, since I still have them. I swapped out the HTM 200s and initially bumped up the levels on each about 4 db (IIRC), given the lower sensitivity of the S2s compared to the 200s. I was able to use one of the speakers stands I had from when they were doing front main duty, but for one side I had to perch the speaker on a stack of boxes as that corner does storage duty I can't easily relocate (the 200 was closer to the ceiling on a small bracketed shelf- too small for the S2).
Watched the last three episodes of Daredevil S1 to start. This show has had a very active and well thought out surround mix. It seemed like, if it's not an action scene, there is almost always some surround content in the form of ambient city noise.
Initially, I questioned whether I needed to adjust the levels even higher, as the backs seemed inordinately quiet. But then an action scene kicked in and suddenly they were way too hot, so I ended up dialing them back to just 1 db over what I had them set for the 200s.
After Daredevil I watched content that was 2.0 so just before packing it in for the night I pulled out some discs specifically to demo some surround scenes.
I started with the first couple chapters of the original Superman, which included Williams score and the Phantom Zone trial (with some nicely subtle ambient echo effects), and then cycled through a few musical numbers from Xanadu.
My takeaway from all this was - while the Sierra 2 and RAALs were *better* than the budget 200's, I didn't feel like they were substantially better when the subject was a flurry of typical action movie effects. The 200s have been just fine and maybe even worked better in voicing out subtle sounds, given their higher sensitivity.
I also can't say that the soundscape seemed substantially more cohesive, as channel panning with the 200's in place has always sounded seamless.
However, when it came to music- whether songs or the orchestral underscoring, I more often noticed and appreciated the difference. I'm closer to feeling like it would be worth it to have RAALS in the back for just that aspect.
It's a bit frustrating. The Lunas would work so much better for me given their size (and front port). I could slip them right onto the shelves I already have in place for the 200s.
At the same time, I already have speakers that are even more substantial than those, that wouldn't cost me anything to keep, but placement is almost a non starter.
I can play with them for a little while, but they can't stay where they are now. They're just too big and heavy. But to sell them off and buy the Lunas, I would be spending more to get less (speaker). When I look at it like that, it seems like the most sensible thing to do is to just keep the 200s where they are. I always felt they meshed amazingly well with the RAALs in front before, and they still aren't that far behind after this test.
I'll probably just end up selling off the S2s and not doing anything for a while. At least I got to satisfy my curiosity.