misposted earlier, didn't read the end. Low volume huh? Impedance is not the spec you want to look for, sensitivity is. You want sensitive headphones, and if you can find ones with impedance of 50 or higher that'd be good. You could also get an amp, but you'd be double amping if the switch doesn't have a line out (that's a bad thing). SR is rated at 112dB, so you want higher. I'm pretty surprised such a sensitive headphone isn't getting enough volume, must be a really weak amp.