The remark about moving out old inventory makes a lot of sense. Thank you for the reply, and for the FlashSoft tip. I wonder how that compares to the bcache Linux module (part of the kernel).
This controller will go into my everyday workstation at home which is a dual-boot system (windows 7 and linux). I currently have bcache over a software-raid. However, using that in windows requires a virtual machine with a Linux guest that shares the volume over Samba (network file system). The performance is OK even after applying the virtual and network layers, but you can probably guess that it's not perfect and somewhat maintenance heavy.
I'd rather pay once for a controller that both systems can use directly instead of buying a software package two times. I bet that FlashCache costs something like 270 USD and even if it performs better, my needs are not that huge. I will be perfectly content with 20-40 MB/s for 4k reads and writes and 250 MB/s for large files. I think the mentioned controller surpasses that easily. Besides, I can use the controller in a file server after some 7-10 years, while the current FlashSoft package will most likely not work with the software in 2020 (windows beyond 10 and probably Linux 4 or 5). In other words, the card seems like a better investment.