Syncthing works perfect. The only issue is, that I have to reboot NAS one or two times per month because it looks like Syncthing or NAS does not respond properly. I experienced something similar in past with Bittorrent Sync also, so I am not sure if the problem is with NAS itself or with additional software.
Because I am trying disconnect from cloud services with personal informations like addressbook, e-mails and so one I tried to install ownCloud into NAS. Unfortunately, current software as MySQL database or webserver installed on NAS prevent Ownloud installation because of old versions of webserver and database software. I was unable find software in requested versions, so I could not install ownCloud.
Finally I decided order Rasberry Pi.
It has been delivered during November 2015 with ordered case, passive coolers and SD card with Raspbian. Installation of software was easy, connection into home infrastructure was also simple. I work with it through ssh connection through terminal on my laptop. Now my Raspberry runs with Syncthing and I plan next step with ownCloud.