Bought the M50W from Heavy Arm in Subang about a year ago. Didn't realise they were your partners until this thread. Nice little store with very polite sales people. Upgraded from the Z623 and the difference is amazing.

The Z623 had almost too much bass even at its lowest setting. Kept getting this boomy effect where even my glass cabinet would rattle for even the simplest noises in games and movies. At medium bass, dialogue seemed to be drowned out by bass. The M50W was an aamzing upgrade. Tight bass and clear mids and highs (well at least to me). Haven't tried an AMP/DAC combo with it but I'm not sure if its worth it to.