The Rega Planar 1 Plus is Rega Planar 1 with an added built-in Moving Magnet phono stage, which means no additional box/cables for an external phono stage. The Planar 1 Plus has Rega's RB110 tonearm and a Rega Carbon MM cartridge. The Planar 1 connects to the audioengine HD6 RCA Input using the supplied RCA cable. No additional cables needed.
The HD6 is a pretty big step up sonically from the A5, has real wood walnut/cherry and a nice metal trim surround for the volume and included grill. Compared to the audioengine A5, HD6 has a 24-bit DAC, a larger cabinet and bass driver, two analog inputs, Toslink digital input, and aptX HD Bluetooth - which has higher bit-rate digital audio and greater distance range than standard Bluetooth.