[Aegir]

Hello, All -
 
Occasionally, shared listening is fun.  I'm trying to match volume with my current equipment, on the cheap.  (Ideally, I'd purchase an identical pair of headphones - problem solved.  I can't do this w/o spending at least $200.  So, until then, I'm looking for an inexpensive fix.)
 
Perhaps someone more technically-minded can suggest a solution?  I was thinking of getting some type of attenuating plug for the high impedance cans?  Perhaps making a plug in device with a matching transformer.  I have basic soldering skills.  For now, I'd like to try to get my 250 ohm cans to share the load with my 600 ohm cans.
 
Here's my equipment:
 
W00-6 Tube Amplifier
Kimber PBJ 1/8" "Y" Splitter
 
Headphone 1.) Beyerdynamic DT770 (600 Ohm)
Headphone 2.) Beyerdynamic DT150 (250 Ohm)
 
The frequency response for both sets are almost the same, but the 250 ohm cans are louder through the Y splitter.
 
I realize that any type of attenuator, or anything else inline will degrade sound quality some.
 
Thanks for you help!