Now with an Nvidia Shield TV, Google Chromecast with Google TV or a Mi Box S, an Apple TV, yes then you can also watch TV with the monitor. But the device has no speakers.

This device would be better than a Full HD TV, but to get a 4K picture, you would have to buy a UHD 4K monitor with HDMI 2.0, preferably with built-in speakers.

This Dell monitor has 4K UHD resolution (which also makes working on the computer easier, because fonts can be displayed razor-sharp) and it has built-in speakers. It doesn't cost much more either. However, it is not necessarily intended for gaming.

Dell S3221QS (31.50", 3840 x 2160 Pixels)

If the monitor is meant for gaming and TV, then this device could do it at 32 inches, it also has speakers, but no 4K resolution:

ASUS TUF Gaming VG32VQ (32", 2560 x 1440 Pixels)