Yea the first link, is for a mini TRS to RCA cable, good for plugging your iPod into your controller/mixer’s aux input or perhaps your midi controller’s output into your laptop’s input so that you can record in a DAW. (audacity is a workable free version…it’s good but you get what you pay for)
You would only need to go this route if your dj software doesn’t support recording your set. I always just record my mixes in Serato Dj or use the 3rd channel on my SL 3 if I’m working in Scratch Live.
The second link is for a USB DAC…from the description it looks like it will only do the digital to analog conversion and not the other way, so the only thing it would improve is how music sounds coming out of your computer. If you were thinking it would make your mix record at a higher quality, you might be mistaken.
That NI audio 2 might be something to look at as it has an audio interface and will allow you to record your mixer/midi controller’s output through your DAW of choice.
I’m not sure about the price, but it might just be cheaper to pay to upgrade your dj software instead, that way you can record from right in the Dj software and then run that wav/aiff file through your DAW to tweak the volume and EQ settings as well as convert it to .mp3 for easier online sharing.
Here’s an example of a mix I recorded in Serato Dj and then normalized and EQ’d in Ableton Live: http://goo.gl/1oL8zP