That's from the AKG website for the K612. That is a somewhat sensitive headphone but also a higher impedance than say a K7(XX) or X2. The website also says it has 200 mW max input power. Something with 100mW or more output around that impedance would be recommended in my experience. You are more likely to damage speakers/headphones driving them hard out of low output source than picking up an amp with "too much" power. You should get useable volume out of a PC but I doubt they will sound anywhere near their best IMO. I am biased as I believe in the use of an amp whenever possible for all of my headphones. YMMV!