Sooner or later ( sooner the better) I'll probably look for a Stax amp ..  the question is SRM252 or SRM323 ?  @Shipsupt : did you compare you 252 to more pricey stax amps ?

252 is a good little performer and will kick the Koss amps butt.  The step up in STAX amps will deliver results but the price isn't necessarily going to tell you which one is better.

Make sure you get the polarity right on a universal DC adapter.

The "loop out" on the STAX amps is nice feature, especially if you've got few amps you like to have set up. 

Good find on the SRM1. That's a good place to start without breaking the bank.  It will be interesting to see what you think of the 404 vs. ESP950, two completely different beast for sure.  Enjoy and keep us posted.

For sure, i will give impressions.  I tried a SR303/SRM323 combo last year and was positively impressed and i really like the 'out of nowhere" refined sound . I prefered my HD800 though. 

I'm still waiting Anaxilus impression about the SR307 vs ESP950 comparison.....

Sorry about that long Thanksgiving week and busy schedule.  Here you go:

http://www.changstar.com/index.php?topic=1819.msg53670#msg53670

About the SRD-7 (it needs to be the MK II version) with the ESP-950. It gives a tad more engaging and lifelike  sound ( w less "plastic" in it) to my ears than the E-90 unit, and/but - importantly - only if you put a good  power amp before it. The box is probably transparent enough to reveal any amp weaknesses. (I am using a very good-sounding  amp with it, as far as I can judge, an AKSA LF55*). That said, I find E-90  serviceable enough. (prolly a tad underrated due to its modest appearance, plastic case, low weight etc). The  difference may be compared to coming from SS to tube amps, to a certain degree.

Notes.
"Routinely" with these SRD units (I used to have a comparable thing driving my old Sigmas, say) I  shorten the protective non-linear resistors in the signal path, since I do not tend to abuse the  units anyway. They are easy to find, look like ceramic capacitors.

A cheap solution is to buy an SRD-7 MK I and add the few components needed to give a "pro" bias  voltage. If one knows the difference between a diode and a resistor it should be doable. One could even probably boost the voltage a little, if for Koss use solely.

I can not listen to the ESP-950 without taking down the level around 1 kHz somewhat through EQ. But  I may be oversensitive to the (often encountered) bump in this area in headphones. I also have Nova  Signatures and they have a much bigger bump, almost unbearable & uncorrectable, so I tend to do not  use them, despite otherwise they may be a better performer, sounding  a tad more hypnotizing. In any case a little EQ at this point cleans up the sound considerably, overall.

I could not use the U.S. 115V supply unit my E90 came with, so I put 3 diodes in series with a an  old 12V adapter that originally belonged to an external HD (or was it a CD burner), I have the house  full of them. This gives 9V and works well. Should be a a tad more powerful in principle, but not that it matter much in this connection, I think..

Finally, the Koss Combo is at home.  .

Is it necessery to give it some burn in ?  From the first minut of listening with the E90, It's good but I'm not so impressed. its seems the sound lack balls, bite, precision. It's a bit too soft for my tastes. Fortunately the FR is good so I think I hear what everybody is complaining about with the E90?

Very very early impressions . Sorry If I'm wrong.

Nope, that's right. E90 is just a functional craptastic amp. OJ tried rigging a new PS for it and still gimped by the circuit.

No burn in needed for these, just time to charge up stators evenly.

FWIW, when I heard the ESP-950 some time ago out of the E90 and the T2, it still sounded to me kind of how you describe it Sorrodje. The T2 offered some improvement, but still a bit rolled at the corners for  my tastes. The Lambda Stax cans seemed to me a bit more lively. I liked more the Lambdas (207, 507, 404 ... and can't remember which other bread toasts).

The ESP-950 cans are quite large and it maybe possible to fail getting a good seal depending on head shape as well. Sometimes I don't get a good seal with some used Lambdas either, but sometimes things work out. Rarely have I had a problem like that with the Omegas tho.