I agree that a sound card doesn't matter. I use a sound card only because I damaged my onboard audio and I pulled this sound card out of a spare PC.
Onboard audio is FINE for 99% of people. I like music and constantly listen to it, however, I don't own several hundred dollar headphones, so I don't feel onboard audio sounded any worse than my Creative Sound Blaster Z sound card which is like $90 new.
This is a PC build, not a PC setup. The keyboard monitor and mouse are not included. This is to be expected.
OS you want to use is entirely up to the user. Again this just the computer, its not software or peripherals.
A console does not serve the same purpose as this computer, so comparing them is needless. Yes, they both run games, but a console cannot do half of the things this well-rounded PC can, or at least not nearly as well. Streaming and productivity are just a couple of examples. Plus, people fail to reason the consoles are so cheap. The games cost way more which is where ms and sony make money. Once you load up games on both, the cost evens out and then the console is far less useful.
I still can't believe toms picked this PSU tho. Even if you are going with a low end PSU, a Thermaltake Smart 600w is $5 more. It is still horrible, but at the very least it has more PCIe connectors, active PFC, and is 80+ white certified.