AlexaBlacki got k240mk2 (if what they say is true about m220 are k240 in different color) and 668b, and both switched to velour pads
They are different even though they look identical.
1) k240 sounds more in your face, while 668b are futher
2) k240 has better bass and mid range responds while 668b has higher highs
3) k240 has softer clamps
Are k240 an upgrade? no. they just sound different