Official comment
YAAAAAAH! DJS!

MAN that software was... something! lol
I'm rocking a Mid-2015 with i7 and 16GB RAM and seldom have any issues with rekordbox, even when testing video performance. I've got over 50,000 songs on an external SSD (I never store my music internal; allows me to move between computers, plus more breathing room on the internal drive). The other advantage to the external drive is if you prepare your content and "export" it to that same drive, it doesn't duplicate the music, just prepares an export database that the XDJ-RX2 could read, so you'd be set to use it as a stand-alone (without the computer) should the need arise.