The easiest way to get 3 channels is probably just using usb. Alternatively you could use a multichannel sound card with analog output or fit three optical outputs to it. If you search this forum for 'camilla dsp' that thread will give you an idea of what can be done.
And right there, ladies and gentlemen, is why people will buy a WiiM.
‘Just use a sub’? And the crossover in the analogue realm, rather than the digital? And whilst some subs have some bass management, many don’t.
And the whole idea of “Just use a PC” is implicitly because you already have one, plug the USB out into a DAC, and away you go.
Buying (and installing) a multi-channel sound card, and buying two DACs to handle them, not to mention controlling from a PC interface (where the term ‘user-friendly’ is ever one you’ll hear from users) vs WiiM’s much lauded interface, is enough to put many off.
Plus, a PC is a PC. If you have one, it may not be where you want your hi-fi. If you want to buy another, then that’s going to cost more than a WiiM. And you won’t be able to control it in its entirety, start-to-finish, from your phone.
I spent years using a PC as a steamer, and it wasn’t home hi-fi, it was a bloody science and technology experiment every time you wanted to play
Please, Please Me.