That case is not very common (I don't live in Greece/Europe), so, I have not personally seen such case nor even have seen any reviews about it.
Based on unconfirmed specs alone, the case is a bit bigger than usual (it supports full sized ATX motherboards), unlike most cube cases that only supports smaller ITX or micro-ATX format. With the Powertech PT-231 ATX cube cases dimensions of H353mm x W236mm x D320mm, it is very similar in size to the Corsair's Air 240 case (http://www.corsair.com/en-gb/carbide-series-air-240-high-airflow-micro-atx-and-mini-itx-pc-case) but can fit ATX and larger components as in the Corsair's bigger cube version, the Air 540 case (http://www.corsair.com/en-gb/carbide-series-air-540-high-airflow-atx-cube-case).
Most (not all) GTX 1060 GPUs are less than 260mm long, so, those will definitely fit in there for sure. Though, there are some GTX 1060 models that are much much longer (like the Asus Strix, Gigabyte Aorus Xtreme, and Inno3D iChill X3) that are about ~280mm to ~300mm+ which might not fit.
My gripes about the Powertech PT-231, basing solely on the photos and specs, is the motherboard *may be* (not confirmed) inverted as the expansion slots/PCIe slots are on the upper portion and the I/O are on the lower portion (as seen in the photo of the rear of the case). It also seems (again, not confirmed) that the left side panel of the case is purely a vent (not a window) where the PSU fan will intake its air; while the right side panel of the case, where the motherboard is located in an inverted position, is the one with the window panel (or may be just a solid panel).
The airflow also seems (based on photos) restricted, and some unconfirmed specs indicate that front and rear fans are only up to 120mm in size, with a side fan only up to 80mm. Not even sure if there are air filters included to prevent dust accumulating inside. I can see that the cabling holes lack rubber grommets.