Boozebuttons explained the set up we used and most of the evaluation was done using the hifiman headphones. That said, the only IEM's I personally own are the Shure SE-846's and the only way I could listen to them was thru the 3.5 mm (unbalanced) output jack of either the Red Wine Audio RWAK240 or the second base (non modified) AK240 we had. We simply copied the exact same music I am personally very familiar with to both players and I moved the IEM jack between the RWAK240 and the AK240. Honestly for the few minutes I listened this way I hardly moved to the base AK240 unit as I was already very familiar with how my source music sounds using this device. I concentrated my efforts on the sound quality of the RWAK240. The obvious difference to me using my IEM's was in the mid-range area (voice). The sound was simply more musically correct and accurately described on the Red Wine Audio website.
I also wanted to mention that Vinnie does a beautiful job with these mods! He is very methodical man. I very carefully inspected the RWAK240 regarding gaps, blemishes or scratches on the unit. I even looked carefully at the base jeweler screws and everything was literally perfect! Trust me if something is even slightly deviated from a factory perfected unit (which I just got last week) it would drive me crazy!!! Yes he is that good!
Also as already mentioned in my previous post and in my humble opinion both units (AK240 and Cord Hugo) are truly current "state of the art" players however that being said, "thank goodness" for this upgrade path (RWAK240). As I would have purchased already purchased the Cord Hugo if this path did not exist and for my application it would have been much more difficult for me to truly enjoy this beautifully sounding unit.
Thanks for the review. Have you try the balance out with some low impedance IEM/cans and compare with the 3.5mm jack?