Arsenal German World Cup star raid?

With the transfer of central defender Thomas Vermaelen to FC Barcelona Arsenal are said to be stepping up their efforts to sign a replacement central defender before the end of this transfer window.
Arsene Wenger is said to be an admirer of Mats Hummels - especially after his impressive performances for Germany in the World Cup, and would like to have a central defensive partnership of Hummels, and Per Mertesacker at Arsenal this season.
Borussia Dortmund are said to want a transfer fee in the region of 25 million pounds. (31 million Euros)
Manchester United are also said to be very interested in signing Hummels.