I recommend that you go with an amplifier which does not inhibit any noise problem since the Proline 750 is an EXTREMELY revealing and honest pair of cans. Feed it with beauty and you will cry with joy, feed it with anything less and you will cry with agony.
Solid State amplifiers seem to go well with Ultrasone headphones. Ultrasone used to sell Rudistor SS amps to go with their headphones. Also, Meier Audio amps are a good match with Ultrasone headphones. Even the small Corda Move portable amp performs very well with the 750. Hope this helps.