TBH, Sony is a very odd company when it comes to audio (strictly speaking audio here, not their other stuff). Every once in a while, they would release something that is like a gem, only to be hidden away with damn near zero marketing.
I've had the liberty of testing the entire Core series package a couple of weeks ago for a good 1 hour (not even long at all, but enough for a first impression) in a Sony store. The speakers were all running off a Sony DN-1060 receiver, for better or worse.
So first off, just purely on stereo imaging with the CS3. I was impressed right off the bat, the neutrality that it offers (something uncommon at this price point) was just astounding. There was very little hint of bloat in the bottom end, the trebles (or even the low-highs) weren't harsh, the mids weren't veiled at all instead filled with detail, the soundstage was wide enough to have a good sense of directionality, and most remarkably there was very, very little distortion at high volumes (again, at this price point, most speakers just starts to clip at 60% volume). To say the least; it all just sounds, natural. What the source feeds is what the CS3 will play, with very little hint of bias in any areas.
I don't know what Sony's goals were with the CS3, but damn if neutrality was what they wanted then I don't think there is another floorstander at this price point that beats the CS3, matches it perhaps.
Next, I tried the CS5 bookshelves. I was fully expecting the CS5 to be decent at best, nothing special but just decent. As impressed as I was with the CS3, I find myself toe tapping again and was fully engrossed with the CS5 like I did with the CS3. Obviously there are differences, the CS5 has a more forward presentation, it obviously doesn't extend as low as the CS3 but it certainly isn't lacking of bottom-end heft. There was good grunt, without overclouding details, punchy yet dynamic. The "super tweeters" though... well, I'm not going to hear 50khz, so yeah... I don't know what to say about the trebles other than it wasn't harsh, though did sound a little rolled off if I had to nitpick.
As for the center channel CS8 and the sub SACS9, I tested a movie (The Amazing Spiderman 2, what else would they play in a Sony store?) with them in conjunction with the CS3 and CS5. So good ol' 5.1 goodness.
First the CS8, I'll cut right to the chase and say that if the core series has a weak link, it's the CS8. Why? Because for as well handled it can be in the fight scenes between Spidey and Electro, it lacks grunt. Yeah, the CS8 can indeed be very clean, without voices sounding muddy or overly fatiguing. But everytime there was a transition between an action scene with voices, the CS8 sounds noticeably hollow and thin. I wouldn't say it is bad by any means, but in comparison the Pioneer AJ-SP22 which is usually the benchmark for entry level center channels was better in almost every way.
How about the ACS9 sub? Sony has never really been one known for quality subs. So I fully expected the ACS9 to sound bloated, muddy, and just be like any run off the mill standard sub you get with overpriced PC speakers. But I was wrong, very. The ACS9 has a solid sense of tactility and but isn't overly aggressive. There's a decent amount of attack, definitely enough to feel the bass-thumping chest. The downside is that the ACS9 won't extend very low unfortunately.
The extension it gets transitioning from the CS3 was impressive however, there was very little sense of disconnect between the main channels. It was cohesive, immersive and everything else except negative. The ACS9 is a solid performer, it definitely won't match up close to an SVS SB2000 (or even the SB1000), but against the overly popular Polk SW10 or Dayton 1000, the ACS9 comes out on top as the more balanced one.
Unfortunately, I couldn't test games. Yeah there was a PS4 in the demo room, somehow missing of its power cable... so, uh..
This isn't a comprehensive review, far from it. As the store demo room wasn't actually that well treated and the placement of the speakers could be better (as well as the fine-tuning IMO), taking all these into consideration I do think the Core series speakers from Sony is a very, very good value buy. Yeah there are slightly cheaper alternatives like the very popular Pioneer AJ speakers, but I certainly do feel and has experienced that the Sony CS package is a lot more capable than the Pioneer AJs. It's just a shame Sony released this in 2014, didn't gain traction at all through 2015 and probably isn't even manufacturing more of them for much longer (I could be wrong, but it feels that way).
For anyone looking to get an entry level, mainstream set of speakers, I don't think you could go wrong with the CS3, CS5 and the ACS9 sub. I'd personally substitute out the center CS8 for something else though.