Got the HDMI coupling risen since I still have a LED TV with no built-in tuner and only one HDMI port on the back of the TV set, among others. Because the TV also is on a wall bracket, the use of the FIRE TV sticks would have been impossible even using the supplied HDMI extension.
By HDMI-coupling is no longer this problem. Now I can simply pull the device connected to my DVB-C box HDMI cable and the FIRE TV Stick connect conveniently using the HDMI coupling it.