If your TV is not enough smart, you can make it more smarter using Raspbery Pi and OSMC software. It will allow watch movies, listen to music and show photos of last trip to your guests. Other option is to buy TV box that will support features that you need. But creating your own media center is more flexible and custom solution. There is most popular media center software called KODI. It can be installed on Raspbian, but better way is to use OSMC or LibreELEC software that includes KODI media center.
All that is required is any version of Raspberry Pi, case, power supply, HDMI cable, micro SD card (I recommend Samsung EVO Plus, 32 Gb will be enough), and some time to install software. Also some remote controller can be purchased to control media center. For stable connection it is better to use wired Interned, if your Raspberry Pi version supports Ethernet cable. Also for storing movies you might need some hard drive. Of course you can store them on micro SD card, especially if it has large size, but this will be more expensive than buying 1-4 Tb external disk.
First of all download OSMC image and write it to SD card. Then insert card to Raspberry Pi and try to boot it. First time can take longer period of time than next boots. That's almost all! After that you can configure wifi, set regions, etc. You can switch SSH support in settings menu, so it will be possible to connect to media center from another computer. Default login/password is osmc/osmc.
After connecting external drive it will be automatically mounted. I recommend to use disk formatted to ext4 file system - there will be less problems with it, than using ntfs drive. ext4 file system was designed for Linux OS and offers less CPU load and more read/write speed.
Next step is to turn on Transmission torrent client. This also can be done from settings My OSMC. For configuring torrent client can use SSH connection. First stop service:
sudo systemctl stop transmission
Then edit configuration file
sudo nano /home/osmc/.config/transmission-daemon/settings.json
And start service again
sudo systemctl start transmission
Documentation about configuration keys can be found here. Transmission client allows to access to it using web interface, by default it works on 9091 port. For example http://computer-name:9091. Configure rpc section in config file. Using this interface it is possible to add torrent files and Raspberry Pi will automatically download content to disk or SD card. Path can be configured in transmission settings file. Also I have configured maximum download speed 1Mb/s and number of connections ~5. Raspberry Pi 3 is not very fast and lot of connections and download speed can slow it. You can experiment with these parameters.
It is possible to open this web interface outside of local network. In this case change password in config file.
Other options to download file to media center is using network sharing (samba client).
Kodi has simple interface with large configuration option. I did not describe them all in this post. Also it has many plugins: for example there is plugins for YouTube, weather or even games. Flexible configuration and lot of functions make it ideal for home media center.