Then I would try a different PSU and possibly motherboard. You could always take your graphics card out and try it in someone else's PC.
Also that card you picked out looks the same as 7900GT think MSI just like to throw GTO at the end
.
look here for other brands:
http://www.overclockers.co.uk/acatalog/7900_Series.html
and some are cheaper Id go with EVGA or BFG