If you look at the Asus specifications, you will see that at least 300W are required. So it's going to be a bit tight.

It depends on the other parts in your pc. I would recommend that you do not do this, as power supplies are rather cheap. If you still have a hdd, then it is certainly not enough. Depending on the cpu, it might be just enough. But you can only find that out if you add up all your devices - certain cpus need 90 watts themselves, so the newer they are, the lower the power consumption will be.