I agree with all that has been said about the quality of the signal chain going in.
 
Yet, I still believe that there are people out there who hear the difference between converters, but those people have their signature sounds and chains that they know exactly what they sound after years of applying them and any subtle difference will become apparent.
 
For those like myself who work in the box (i.e. without a superb sounding analog console in between) I only get to hear the signal after the whole AD-DA conversions happened. So I assume if you give me slightly different converters, wouldn't I adjust slightly different to come up with something similar ????

I think it would be interesting to have some of the posters who claim to have such wonderful hearing actually take Ethan's challenge and prove that they can truly hear half of what they claim.  Talk is cheap, can you even tell the difference between something that has passed through a mid-range audio AD/DA setup 10 times?  Post your findings here and lets see how well your ears past the test after he publishes the answers.
 
Glen

I recently needed to make a location recording. Something I don't often need to do. The only thing I had was my old zoom handheld H4.
 
The H4 is one of the one of the older ones and you can find them on ebay for a pittance. I went to the location to experiment with it. Honestly I didn't have my hopes up very high. I was fully expecting to need a better rig for the job.
 
I used two condenser mics plugged into the xlr ports of the zoom with the H4 on battery power. After I had the gain staging correct I was blown away by the quality of the recordings. I can't imagine these converters being very good, yet the sound with no outboard preamps was amazing.
 
One thing I've noticed recently in my own recordings is I get more sheen using the highest bitrates and resolutions. In the case of the H4, it can record in 24/96 with phantom power. I suspect that if you ran the less expensive converters up to the highest resolutions you might notice a difference over 16/44.1. Higher resolution won't get you the exact sound of those more expensive converters but it seems to help.
 
I still might be getting another field recorder but I was blown away by the quality of the H4 for what it is.
 
As an FYI, I have noticed some killer converters at a great price but most audiophiles are missing it because it's marketed to photographers. Check these out- 
 
http://tascam.com/product/dr-70d/
  
http://www.amazon.com/TASCAM-DR-70D-4-Channel-Audio-Recorder/dp/B00OY6718K/ref=sr_1_1?ie=UTF8&qid=1463399677&sr=8-1&keywords=tascam+dr+70d
 
http://www.amazon.com/TASCAM-DR-60DmkII-DSLR-Audio-Recorder/dp/B00MIXFBL0/ref=sr_1_3?ie=UTF8&qid=1463399677&sr=8-3&keywords=tascam+dr+70d
 
You can make great movie sound if you have the matching camera or they make excellent field recorders!

In my experience, it is the preamp and the (headphone-)amplifier which makes the difference. Even low budget interfaces like the scarlett have "ok-isch" converter. But the analog parts of the cirquits are expensive. Using an additional preamp as well as a headphone amp changes the whole experience.
Try to use a really good DI (Neve RNDI) instead of the HZ input of the interface: There is the real difference. And this gear will stay in your studio for generations of audio interfaces...