This might be the answer, although it is only 80W.
You would need to check how much current each line draws.
+5V: 8A Max, 10A Peak
+5V STDBY: 1A Max, 1.5A Peak
+12V: 3.3A Max, 4A Peak
Power supply overall efficiency >90%
Would be alot better than DC>AC>DC
From what I've read about it, it only takes
+5V STDBY: 1.5VA
Call Opus and find out if you can get the 80W with just 12V and 5V SB.
It should produce:
+5V STDBY: 1-1.5A
Changing the connector from 8 to 6 pin shouldn't be a problem.