I buy and sell a LOT on ebay. I can tell you that "Power Seller" means nothing more than that the seller maintains a certain level of sales each month -- it says NOTHING about whether or not a particular seller is honest, etc. In fact, ebay holds powersellers to a LOWER feedback percentage standard than regular sellers!
When buying on ebay, 99% of the time the games that say "English subtitles" or similar are illegal copies. You'd be better off buying the game in a regular store, or here on GB.
On ebay in general, it is recommended that you not purchase anything from a regular seller with a feedback any lower than "body temperature" (e.g., 98.6% positive feedback), and higher than that is, of course, better. When purchasing from a powerseller, it is recommended that you buy only from a powerseller with a feedback percentage of at least 99% positive -- they do so much volume that it should be easy for them to maintain a minimum
99% positive feedback rating, if they're any good at all.
Just for comparisons sake, I've been an ebay member since December 2002, I have 440 total feedbacks (426 unique ones), and a 100% positive overall feedback rating -- never received a negative or a neutral. That's because I'm honest (and my prices are decent, I package very well, etc. -- but mostly cause I'm honest!). Which is not to say you should avoid an ebayer with a couple of negatives or neutrals, so long as the overall percentage is good, and so long as s/he responded to those comments in a professional manner.
Hope no one minds the tangent, lol! It's just that I'm very active on the ebay "Answer Center", so I like to share my ebay knowledge.