The CPU multiplier: an "S" part has a lower max CPU ratio (set Turbo bins aside).
If you look at some reviews, some of the AIOs don't do too bad. Cooling is adquate and for some, noise level doesn't seem exceptionally bad? Check this one out?:
I don't understand what I have to look at, Frostytech isn't a reliable source with reference to noise levels, their noisefloor is too high and their methodology is unclear, so those numbers are mostly of little or no usefulness.
The H60 doesn't do too badly? I was comparing to the LP noctual heat sink. Is your preferred/fav. heat sinks in that list by chance? How do they compare?
I prefer big chunks of metal with fan spinning at most around 600rpm: up to now that's the most effective way to cool at the lowest noise levels (even if it's not neither the most effective way, nor the most efficient way to cool a CPU).
Broadly speaking, any moving part emits noise according to the way you drive it: so any AIO can sound either unbearably loud or much more comfortably.
Said that, the radiators are high impendance structures, so the airflow need to be high in order to be effective. When the flow is tiny, so when the fan spins low, the cooling prowess drops, and the higher the impendance is, the more it drops. Even the relevant noise signature is less favourable, because the "quality" of the noise of the air spilled through an high impendance structure is worse, making the noise more "noticeable" at human ears. Simplifying those are the main reason an AIO can't be really quiet and effective at the same moment: it worths to mention that with very efficient CPUs (like Haswell) often even at moderately loud noise levels lots of AIOs can't really shine over their air-counterparts (as seen in some reviews of low end ones, as Corsair H60 or H75). If you look at the performance of a 100$ Cooler Master Seidon 240M (pump at 7V), it shows a 54°C rise over ambient with a noise level of 15dB, a premium low profile but low performance cooler as the 45$ Noctua NH-L9i at the same noise level shows a 61°C rise over ambient, while a tower heatsink like the 35$ Scythe Kotetsu shows a thermal rise of just 38-39°C.
I don't know much about all those brands/models but I prefer a small form factor system. I've used big towers, mostly mid-towers but I want one smaller now.
So, if you already know what you want, what are you looking for, from us? By the way, not all the SFF enclosure need a low profile cooler.
My EVGA card is pretty quiet. Maybe above the gtx 750 series, they are noisy but it only has the one fan and power consumption isn't much.
If you perceive your EVGA as quiet, more probably that not you don't need any advice on how quiet any cooler can be: you probably won't perceive them as not quiet, and any Silverstone TD03, Corsair H75 or H60, Enermax Liqmax (or similar products) should work well for you, despite they are the quietest option or not. At least it's my opinion, right now.
imo the crippling of s parts is not as big as a factor as some seem to say. its all about the cost per core and clock speed. i found an s part that was on sale cheaper than the regular part. i have no regrets on my purchase at all. ymmv
I was not talking of any price/performance ratio, but just of cooling/performance one: an S-part isn't noticeably cooler than a regular SKU, so it isn't mandatory to have a low noise system. But either it won't hurt, you just trade off some slight less performance for some less heat, usually without any substantial advantage, cooling wise (that's my point). If you spare some money, it's a welcome bonus.