So that provides 240W on the 12v rail (20x12). You'll definitely be cutting it close but it may work with that PSU. I'd say give it a try and if you run into stability issues or it simply doesn't work, then get another. One thing to note, running a PSU at or near it's limits puts a lot of stress on it, when (if) it starts running the fan very loud, you'll want to look to replace it soon