I wouldn’t say this is a straight progression from the HD6xx. The HE-560 and Elex are technically competitive with each other, but have different characteristics. The biggest step up is build quality: HiFiMan cut every corner except the drivers while Focal spared no expense on the frame, hardware, and pads.
I’m listening to the HE-560 on the P20 as I write this – it’s really, really pleasant! This may be the best <$500 combo on the market.