Maximum Micro SD Card speed class worth buying

[badelhas]

I currently own the HTC One M8 and believe that all micro sd speed classes work with it: UHS-I U1, UHS-I U3 and UHS-II U3 (the fastest available). But the whats the maximum speed this Snapdragon 801 SOC allows? What´s the maximum speed supported, when the SOC reaches it´s top speed?

Could someone with any of these these cards please perform a speed read and write test so we can see if it´s worth buying the fastest available or not?

Cheers