Originally Posted by Azure
Many people here consider that the biggest difference in sound quality is between headphones, right?
Ah I see where things went wrong. Headphones gives the biggest difference in sound presentation not quality. Which is really just saying that a Grado and Senn sound different in an obvious way but in presentation not quality.
Its about balance, a Senn 650 is wasted on an iPod just a Merdian G08 is wasted on iPod buds. Both of those scenarios will sound awful since no one piece can rise above itself. For your rig, no matter how much you dump into amps and headphone neither can up the quality of the source's feed. At best they can do no harm and in the cans case alter the presentation in a hopefully preferable way.
Given your impression I'd guess the M3 is doing just that. Its not changed the source's presentation, but has improved on the faults of the stereo amp by providing better control and speed in the bass.
The bad news is deals in the source market are scarce. You really either need to be running a PC rig where there are deals to be had or spend to get where you want. In my opinion the quality differences in the sub 500 range are more sidesteps than upgrades and in the 500-2000 range you get some nice rewards for your dollar and then diminishing returns kick in 2000+. Year matters too. Last year's 1000 player could very well be this year's $500 player. Sorry
I'll add to that, that I think a 4:2:1 ratio works pretty well in headphones. So for your Sony 5000(~350?) you're looking at a 1400 source, 700 amp and the 350 for the Sony to hit dimishing returns. Lots of choices on AudioGon for sources in that range, SinglePower PPX SLAM, HeadAmp GS1, Mapletree Ear+ HD, HeadRoom Desktop, Corda HA2... for amps. But start at the source. Otherwise you might as well be building a system around an MP3 collection
Oh and for amps and sources buy used, let the rich guy eat the cost of retail
Looking at your profile though... the Sony is a poor choice for electronica. You'd find the Senn 650 or Beyer 990 far more involving for bass rich, melodic rhythum. Deja Vu for today but Massive Attack through the Senn 650 is an experience