To double glaze or not to double glaze..That is the question

Hello fellow sound geeks. Let's play a game called - Help me make decision! I have built some killer doors for my new studio and am now about to set some glass in place. I have two options; 1 - The tried and true, double glaze system. One pane of 15mm and another 18mm (both angled) with an 60mm air cavity in between. 2 - I have a friend in the glass business who can get his hands on quality laminated 40mm glass left over from a previous job. Because of the thickness, I'd only be doing a single glaze, installed on a slight angle. Now, I'm pretty sure the double glaze way of doing things would most likley yield better results but I'm talking like a $600 saving if i go with the 40mm stuff. It's time to play dudes! What's the better way to go?

Here is a good read about that: http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd240_e.html

..crosspost.....

Yea...he did it like everywhere! But this was my first time seeing it so I didn't drop no buggers on it. :)