Yeah, you are both right, it was a surge protector. And the PSU is a 1.6 Delta.
I borrowed an oscilloscope from a friend and checked the voltages on the PSU connector, and it appears to be working correctly (blue wire ~3.3V, orange wires ~5V). I then checked the collector on the transistor next to the Xyclops chip (as shown at http://www.llamma.com/xbox/Repairs/1.6_Xbox_no_power.htm
), and got a reading of only ~1.7V. So, I ordered a couple of those transistors and will see if that fixes the problem.
What concerns me about this is that I never opened my Xbox prior to my problem, so I don't know what would cause the transistor to go bad (assuming that's my problem). Good thing is, if I am able to fix it then I will finally be able to mod my Xbox since the warranty is no longer an issue!