My room runs a little hot, bad airflow from the vent. I average around 35-40c idle and 45-50c when gaming. I've only tired flipping the CPU fan from intake to exhaust which helped to stablize the temps.
From the reddit forum he said to expect the 560 (3-slot) a week or two after release of 550. Here's also a handy breakdown to confirm your suspicions of the 140mm fan.
SM550: 2 slot, air cooled (2x 120mm fans)
SM560: 3 slot, air cooled (2x 140mm fans)
SM570: 2 slot, 240mm AIO on top + 2x 120mm...
Here's the ebay listing. Guy's asking $700 now. https://www.ebay.com/itm/NFC-Systems-SkyReach-S4-Mini-Buyer-chooses-powdercoat-color/183715938245?hash=item2ac652bfc5:g:1qIAAOSwF0VcHw6N&frcectupt=true
IMO, the listing is bogus. Calls out stock photos and 2-3 week to process. Guy is probably...
Sand, prime, first coat.
Finer sand, second coat.
Rinse/Repeat till desired finish achieved.
Apply top coat/gloss.
Sand, second coat.
Key is several light coats not laying it on like painting a wall.
Honestly I would look for a powder coating instead. My last case was a massive...