I've had my headphones, Sennheiser HD 598 Cs (closed back), for over a year now. I'm pretty happy with them, but lately I've been listening to more music and I've found that even with windows volume set to max I can't quite get music as loud as I'd like. Is there any way I can raise the volume? I'd assume I'll have to buy some external (or internal) hardware, as I am using onboard audio, which I figured was enough to drive these headphones to their max potential.