You don ́t necessarily need to get a new remote control, but you can use either the HDMI CEC adapter or Flirc USB adapter and pair it with your existing remote control.
If you have a modern TV, a HDMI CEC adapter allows you to use your existing remote to send key presses to HTPC via the HDMI interface on your TV.
If you have an older TV, or you need more flexibility, Flirc remote companion is a great USB adapter that turns IR signals of any remote into keyboard commands.
I have been testing Raspberry Pi and HTPC with the HDMI CEC adapter to control the Kodi with my TV remote.
While the HDMI CEC adapter works fine for the predefined keys, I needed more flexibility to map custom shortcuts and buttons (e.g., full screen mode) with my remote control.
If you want to use other applications on a Windows-based HTPC, such as Steam Big Picture then, unlike the HDMI CEC adapter, the Flirc allows you to control any application that supports keyboard commands.
Furthermore, if you have multiple home theater devices, a universal remote is a must companion for the Flirc adapter.
Logitech’s Harmony remotes, are excellent for controlling TV, A/V receiver and HTPC with one single remote.
You can use a universal remote together with a Flirc device. The IR receiver has to be located close to TV to have a direct line of sight.
I would recommend to set up the remote so that you can control the volume on the A/V receiver while other buttons control the HTPC.