"Seaview..." Did you mean "Seasonic?"
Assuming you will be playing games, I believe you can find a HD7850 at the high end of your range, and a HD7770 at the bottom end.
Make sure your system has a magnetic hard drive in it also, if only to store an image backup of your OCZ Sandforce SSD.
Haha yes, Seasonic it has been a long day. Looking into both your recommendations now