I am convinced the PSU is spec'd and working for this card and therefore not the problem.
Just to be sure I reset the BIOS, installed the XFX card and tried both DVI outputs, bearing in mind one could be DVI-D as I have one monitor with an adapter.
Still the same problem. 1 long beep 3 short - with a beep shortly after that.
I swapped out for the old 3870 and it worked again - typing this on the problematic computer.
I am completely stumped on this - have heard that Asus utilities can interfere with certain cards - highly unlikely unless its express gate or something.