It could be OK. If you look at AMD's example figures and round them up a bit for a little extra margin, then you get something like this:
Volts Amps Watts
+3.3V 8A 26.4
+5V 18A 90
+12V 16 192
Which comes to 328.4W, well under 400W.
Now, most power supplies have a limit to how much power they can take off the +3.3V and +5V rails at the same time. A representative figure for a 'bargain' 400W power supply (which this one seems to be) for this limit would be 215W. The sundry voltage rails (-5V, -12V and +5VSB) take up about 20W. That leaves 165W (13.75A) for the +12V rail if the +3.3 and +5v are at their limit.
However, for the specific example above, the combined output for the +3.3V and +5V rails, (26.4 + 90) only comes to 116.4, so there seems to be a fair margin from 215W there. That means that the +12V rail will not be limited to 165W. In fact, it could expect to be able to draw 400 - (116.4 + 20) = 263.6W, which is within the 300W capacity that the figures you quoted suggest (12V x 25A = 300W). 263.6W is equal to 21.97A at 12V, so it should be able to supply 16A easily.
This all depends on the power supply meeting the specifications you quoted. The cheaper ones tend to be a bit optimistic about their capacities, so with a caveat on that sort of consideration, the power supply looks as if it could do the job. I could only find five hits on Google using 'ibest gold power supply 400W', so you couldn't say they are famous. Also, none of those hits gave any current output specs for the various voltages.