No stability issues without the 3-ohm resistance. I have tested that the added resistance only alters the frequency response with
lower impedance headphones. I have some customers with 8-ohm IEMs (I forgot the make/model), so having 3 ohms on the output there WILL alter
the flat frequency response. So if you want it the flattest and more accurate, the lower OI is better.
Not sure if some would prefer the altered response that some added OI gives - I guess it depends where in the freq. response the sound gets altered, the headphones
you are using, your personal taste, etc.
I hope this helps,