Thanks again for the advice.
My current headphones are more or less standard style for general use.
The impedance is 40 and the frequency response is 20Hz-20kHz.
On the other hand, I do have some ER 4P IEMs, which I find to be VERY flat. And I mean that in a good way. They are just under the ER 4s models. Fantastic in ear monitor/buds. Sadly, there is a slight short in the right channel, so I will have to get them repaired.
Their bigger brother, the ER 4S, are actually designed specifically for that purpose, and I would say these are damned close do to the flat across the board sound I hear from them.
20Hz to 16Khz +/- 4db.
Thanks again.
That being said, that might be the best overall choice here.