It's not my DAW. I was referring to dB(spl) whereas your meters are in a different form of dB. I believe dBv is a common unit on meters. There is another unit that is common, but I can't think of it right now.
essentially when you see that 6db boost on your screen or the meters on your mixer, you're seeing a doubling in power, not SPL. You need 10 times the power to get a 6db boost in SPL. A doubling in power only gives you 3dB.
Try your same experiment again, but instead of looking at your meters in the box use a dB meter. You can get one from radio shack for pretty cheap.
I went to school for recording for a while and learned this there. I had never tested it before because it made sense when I read it, but I went ahead and tested it just in case my book and my teacher were wrong. They weren't.
I guess I may have been confusing when I said apparent loudness rather than dBspl. I did that because I didn't think that most of the average home recording guys would even know that there were different units of dB and thought that apparent loudness would be more clear. I guess not.
If I wasn't clear enough, you can learn all this and more in Nika Aldrich's book. It's called Digital Audio Explained for the audio engineer. He is able to explain it in a much more concise manner than I.
http://en.wikipedia.org/wiki/Decibel has good info, but it's not as easy to understand as Nika's book is.
also, just for future reference........ A sine wave can only be perfect in theory.