Hi
A few questions to S3 users:
1) is it possible to place four of these in a small room (15-20 m2) without AC and work comfortably there during summer

? (in other words, how much heat and noise these devices produce?)
2) I've got one Toughpower Grand 1200W - will it be enough for three S3's ?
3) how it goes with overclocking and how does it affect ergonomy (noise+heat and increase in power consumption - see 1) and 2) ) ?
1) possible, yes. Practical, no. Four ants will dissipate 1500 watts. That's more than a typical hair dryer running at maximum. A room of the size you mentioned would get uncomfortably warm in a few hours without A/C unless you get get significant airflow through it. I've had 1400W worth of mining gear in a 12m^2 room with no A/C; there is no way I would have worked in there due to the heat.
Don't make the mistake of thinking the S3's will be "silent". Dissipating 200W per blade (400W per device) is like a GPU at full load. The larger fans on the ants will of course not nearly be as loud as a GPU, but you will definitely hear them. Whether or not the noise will bother you depends on your tolerance.
Hopefully within a week or so we'll start getting reports from customers who have actual units to report first-hand on these questions and more.