That is actually uncorrect in most clubs you will only find RCA to connect to the house or PA mixer and for home studio use RCA is also fine and you can spare the DJ mixer. Also there is nothing inherit cheap about RCA, it depends on the manufacturer and you can also get cheap XLR in a 50 bucks Chinacontroller that sounds way worse… but what do I know I have only DJed for 25 years, so you might have more experience than me 🙂
Nonetheless if your heart is set on the A6 by all means go for it however the Turntables you posted are utterly bad. Honestly the RP-7000 is as low as I would go that is why I recommended the AMX, save money on the mixer side go for a full solution and invest in good turntables.
Now turntablism is a lot about hip-hop and hip-hop (even high class produced) is not always beat correct (aka BPM will vary slightly through the song), this is why we recommend Serato as it has a so called flexible beatgrid. Traktor only has a hard beatgrid and will not do so well with these kinds of music, but whatever your mind is set on.
However you still will need somekind of controller with Traktor if you want to use some features and not always click on your laptop to load things (which looks kinda unprofessional) so one of the NI addon controllers will still be needed.