I love the MDR-7506 headphones for their price point and audio. My needs have changed and I need something with the same audio but sans wires (exposed or otherwise). Thanks! I can go higher, but believe in cost containment.
Sennheiser has as much experience with wireless headphones as any company. There are a few models available for $150 or less. These are a "closed back, around the ear" design as are your 7506:
http://www.amazon.com/Sennheiser-160-Digit...s/dp/B002SOU2Y0 (http://www.amazon.com/Sennheiser-160-Digital-Wireless-Headphones/dp/B002SOU2Y0)
You may want to visit head-fi.org for detailed specs, user opinion and comparisons.
You might also consider a D.I.Y approach.
I've been messing about with various inexpensive Bluetooth devices recently. Much to my surprise those ubiquitous little boxes you see on ebay and amazon for ~$15 work really well.
Some thing like this. BT Receiver (http://www.7dayshop.com/7dayshop-bluetooth-audio-receiver-bluetooth-enable-your-hi-fi-dock-or-car-stereo)
Look around for the best price. They are all the same except having different co. stenciling or various colours.
I use a pair between a Sansa Clip and Senn HD25. FiiO E5 in between at the headphone end but only because I have one, it saves a connecter and extends battery life overall. It easy to make a neat connection with some velcro and a bit of ingenuity.
Quality is allegedly not quite up to CD. It's certainly pretty close though. When I first set it up I was instantly impressed. Good enough without any fiddling around. I also have more expensive units from Sennheisser and Belkin which seem to have slightly better range but don't sound much, if any, different. The cheap separates are better than the BT built into my laptop (ASUS ViVoBook) and BT speaker Antec SP1.
If you like your existing headphones and want to replicate their feel and tonal balance, you could continue to use them by adding a Bluetooth receiver, plus a transmitter to your audio source (if it doesn't already have one built in). Here's an example, not that I have any experience with this particular one:
http://www.amazon.com/TaoTronics%C2%AE-TT-...r/dp/B006IJJH7O (http://www.amazon.com/TaoTronics%C2%AE-TT-BR01-Bluetooth-Headphones-Transmitter/dp/B006IJJH7O)
Edit: Oh, I see my bluetooth idea has already been suggested while I was composing my post and searching for a link.