Nihil,
Yes, you're correct. My current system is an Athlon processor, but the PSU is a 400 watt with both the regular rectangular power connector, AND the newer square 4 pole connector.
Don't recall the brand of the PSU (and if you could see my setup, you'd understand why I'm not in a hurry to reopen the box to find out!)

If I get to it on Wednesday, I'll check out the PSU then.