then at home using itunes I use the D-Zero then my Ultrasone Pro 900, BrainWavz HM5 and HD650.
Should I give this baby up.? and upgrade or what i have now is good.?
save up another hundred or two and look at the HP-p1 and CLAS range of devices.
They bypass your Apple devces DAC and use their own. The HP p1 has both a DAC and an amp while the CLAS is only a DAC
Yes, I agree with that, the bottle neck of your rig is the internal DAC of your iPod.