I would say more like a D5 PWM capped at ~2500 rpm, since XSPC uses a PWM D5
The point being, the Swiftech pump moves approximately 1gpm with 2.2m of head pressure. The D5 is capable of moving twice the amount of liquid with twice the amount of pressure at it's maximum. In a smaller loop (up to 3 blocks), the difference would be negligible, if anything at all. As the loop size increases, the D5 would become advantageous.