Are size, aesthetics, noise and price also a consideration?
As Daniel said, it seems many motherboards no longer have an SPDIF output connector as standard although many do have a header to which you can attach an SPDIF output connector that is often included with motherboards or can be purchased separately for a quid. Failing that, buy a PC that meets your needs and then add a sound card with an SPDIF output. I felt that the sound from the output from the SPDIF on my Asus Essence PCI card was better than the one on my (8 year old) motherboard but that may have been expectation bias. It’s analogue output was superb.