I'm looking to buy a second-handed amplifier to couple with my Benchmark Dac 1 USB. My budget is around $400 maximum and the sound I'm looking for is like LYR. Warm and powerful with Kokia's (a japanese singer) voice. However, all I have are low impedance headphones (K550 and w4r) so the LYR's background is noisy and unacceptable. I don't have much knowledge about amplifiers, so I think the best way to find an amp that suits my need is to ask you guys. Any help would be appreciated.