A Naim DAC V1 is certainly a potential solution but I am prepared to pay for a more expensive solution, such as the Naim DAC, if it offers a clearly audible improvement.
I've never previously paid much attention to the audio facilities on my PC but a quick check shows that I just have basic on-board audio with simple analogue line-in and line-out phono sockets. To use a Naim DAC I might therefore have to buy a sound card to get the required SP/DIF output. We appear to have some differing options here as to whether it is worth spending money on anything more than a basic card. If extra money just buys a better DAC in the card, then that would appear to be wasted expense.
However, buying a sound card might not be the best solution. I have read some very positive reviews of the Musical Fidelity V-Link 192, an audiophile-quality asynch USB to SP/DIF converter.
Incidentally, to get a DAC demo in a hi-fi store using my music files and MC18, I would need to take along my Samsung Chronos laptop. This computer's normal audio (and video) output is via HDMI, which would require a converter device to drive a DAC via optical or SP/DIF. Such converters do exist but not at a trivial cost. Perhaps I should look for a dealer that can also demo the Musical Fidelity V-Link 192, or something similar, so that I could use the USB output of my laptop.
Or I could buy a streamer...
David