I use Sennheiser hd 650 headphones which are known to need a good amp for them to drive/perform at their best. The headphones have an input impedance of 300 ohms, 103dB sensitivity, and a max power rating of 500mW. If I'll use a Presonus Studio 68 which has headphone outputs that have an Impedance Working Range of 32Ω to 300Ω and Maximum Power - 150 mW/channel (56Ω load). Is it enough to drive the Sennheiser hd 650’s without buying a headphone amp? Will they give out correct and flat sound in all frequencies without deviations and distotions?