You hae an STX but you're using a USB soundcard???
Try plugging them into the soudncard.
you mean molex?
if you can afford a £260 headset, surely you can afford a £1 cable?
what do you reckon to the mmx300?
Definitely fix your STX and power them properly. Although the MMX300 is "only" 32ohm it is actually a pretty insensitive/inefficient headphone. Impedance alone doesn't mean it's easy to drive.
Yeah, sometimes I wish there was a bit more bass coming out of my headphones but then I notice that I can hear every note in the music so soooo clearly and I forget about the bass.