[yklee118]

I used to own a Grado SR125 and I can say that even with the low impedance of their headphones, I amp them due to sonic differences.  Without amplification, it is good with dynamics and instrument separation.  Once mated with the Little Dot MKI, dynamics, sonic instrument separation, and overall listening experience is further improved to the point that I will not want to go back. 
 
Sold the Grado since I have rather large ears and the SR125 was rather uncomfortable after about an hour of listening.
 
Hope this helps