Budget DAC/AMP for HE400SE

Got an HE400SE from marketplace for 6000BDT (50$). But I don't have much knowledge on DAC/AMPs. What should I go with? Currently powering it through my motherboard port and it is NOT LOUD AT ALL. A few guys suggested me to get the K11 R2R but that is not in my budget range. But I saw that there's a K11 (Non R2R) that's significantly cheaper. Should I just go with that? Or is there is any other good alternatives in that price range? Budget's 100$ (Audio gear cost much higher in my country compared to it's normal price btw, and awful stock as well)