I doubt there's really anything anyone can do. But I thought I'd post here to maybe shed some light on "Xtrememiners.net". First of all they've stolen over $200,000 so far.

They are clearly a fraud, and I stupidly sent them $10,000 worth of bitcoin about a month ago. I've come in contact with several other people that have been scammed, and managed to get some info on them.
contact with. They claim to be selling BTC Asic miners, but in reality they, their company, and their product do not exist. They make a good job of making them anonymous/unreachable as well.

Heres the small amount of information I have on them:

ISP: Affinity Internet (Now a subsidiary of Hostway Services)
Domain Security: Hostway Services
Web design service: Wix.com
IP: 10.60.103.211 (Blocked with a proxy) Public IP: 216.185.152.159
Main Bitcoin Wallet used to Launder funds: 18YZ4gSS8n84w9WY57nUW4UQFSQypMb7SV

I've tricked them several times into calling me, so I could bluff/scare them into giving my BTC back, or atleast shutting their website down. No dice. Both times a young woman answered the phone, and gave me a bunch of vague answers to rather probing questions (Why don't you have a VAT, Who is Mr.Berg, etc). The second time she called a few minutes later answering to a different name. I called her out on it, and she became panicky and hung up.

The information listed in their Impressum is false, and I have strong reason to believe they are based out of the U.S. based both on domain (.com/.de) Lack of business registration for Germany, and information gained through calls made to them.
I have tried getting information from Wix.com/Hostway Services/Affinity Internet, but they all say they cannot release information without a court order. I have tried taking this case to law enforcement, but no one has taken any action against these fraudsters, probably due to the murky nature of legislation regarding the currency.
If anyone could offer advice/help, I'd sincerely appreciate it, but I understand at this point I, and the other victims of the scam, pretty much just learned a $10,000 lesson in life.

Yeah I got scammed by Xtrememiners.net too. Tried to get my 9.78 BTC from them back as well, as was told that they couldnt give a refund because my order was already being processed. Yeah, BS. If anyone else has been scammed by them, I suggest you report it to Hostway Services (the company that hosts the server in Austin, TX) and file a report with the FBI. They've currently been working with redditors on the sheep marketplace incident.