[Sovelin]

I really doubt this is an issue of low quality audio, sound signature, poor product, etc... The most glaring thing you stated was the onboard audio of your laptop. It is absolutely terrible. I don't even think it could power skull candy (brutally honest here). Yes, you would notice an improvement with your iPod. You would notice a massive improvement with a good dac/amp combo. M50 is wonderful, but only if you treat them well. Feed them garbage and they will spit it back out at you.
 
For example, I purchased the xonar essence stx for my desktop to power my DT770. Now if I plug my headphones into my iPhone, I can't even listen to an entire song before ripping the headphones off. Source makes such a huge difference. I actually had to buy a different pair of cans for portable use and my DT770 never leaves my desktop.

 

[HolyCheese]

I'd suggest a FiiO E10. Much better than my already pretty professional (and in 2004 $300 costing) soundcard. But don't get them for the bassboost. It think there might be better things out there. 
 
My Cowon J3 for example turns these headphones in true basscannons with great quality with the Mach3Bass eq on.

 

[musubi1000]

203s are fun cans but extremely dark where it sounds like the percussion is in the backyard. You can hear the extension but just not as prominent as the bass side of things. The M50s should be like 3xs brighter. As people have mentioned the M50s need like several hours like over 100 to settle. They still won't have bass comparable to the 203s. But everything else will sound in better balance. The M50s still one of my favorite cans as they are more than capable and versatile with dynamics and resolution. I always hear so many people not liking their sound card. Try borrowing a friend iPod or player and see if you get any improvement.

 

[balancebox]

the two M50 I order from http://www.soundprofessionals.com/
 
comes in a teal white box
 

 
shouldn't be blue
 
one black version straight I order a year and half ago
 
and a month back I order the Limited edition both comes in teal box