Curious as to why 5 ohms would be a negative?
As a general rule for bass control:
Headphone Impedance / Output Impedance >= 8
With a 5 Ω output impedance, that typically works well with headphones of 40 Ω or more. Anything less and the bass response will probably affected in a negative way (looser, woolier, etc.) and is especially bad with multi-driver earphones, where the phase linearity and output impedance values can change a lot based on the frequency.
Like so: http://rmaa.dfkt.tk/Comparisons/32%20Ohm%20Multi-Armature%20-%20Cowon%20J3%2C%20Sansa%20Clip%2B%2C%20Sony%20A845%2C%20Hifiman%20HM-801.htm
or
http://rmaa.dfkt.tk/Comparisons/Hifiman%20HM-801%20-%20Impedances.htm