Expert reviews for Sennheiser HD555 headphones can be found at Test Freaks. They also will give you the user reviews too. It really takes both reviews to make a good decision on a product like this.
Reviews for Sennheiser Wireless Headphones can be found where the headphones are sold. Amazon, Best Buy, and Walmart all have user reviews. Consumer Search is a good place to look for expert reviews.
HD555 Sennheiser headphones are available from a number of online retailers such as Amazon or Newegg. Additionally, any local stores that carry high-end stereo equipment should also carry these headphones as well.
Sennheiser has quite a few gaming headsets to choose from. Some of the best ones to choose from include HD555 and PC350s. The variations come in with the sound quality.
Not without an adapter. You could either go out of your tv/stereo system via an RCA/3.5mm adapter. However the MUCH better option is the Astro MixAmp, though it will set you back $130.
The A50 for a bit extra you get the sound quality is almost unmatched not to mention I've sold plenty of headsets at my job and being a small time stream I would recommend them to many. They are hard to find right now but you might give this a try yazing .com/deals/astrogaming/Shadden. they offer some good prices and free shipping.