Optical in requires digital to analog processing, and likely decoding of surround codecs. In the world of encoded digital audio, optical is now legacy under HDMI. Your PS4 will send significantly more audio data over HDMI.
Many brands, such as Onkyo, sell surround sound/home theater kits within your budget. Soundbars and similar compact solutions tend to include optical/digital ins as well. You are not required to search within "computer audio" solutions.
Sound bars do if that's a form factor (shape) you are comfortable with.
EDIT: Failed to see the 1st responder mentioned sound bars.
At that price range, you will not notice any difference between "standard" DTS and Dolby Digital versus high resolution audio formats. So I wouldn't be too considered about the limitations set forth by using Optical (S/PDIF).