How much value lost when trading in?

[tmfs]

This might be a stupid question or unanswerable but I'm going to try anyways. I have a 2006 Acura TL and I love my car, BUT the other day when looking with the fiancee for cars we test drove the new 2007 4 door G35 and fell in love with the car. It's pretty sick, especially with the tech package. I know it's not the smartest financially to trade in my car for a new one, but say I do how much extra money am I really going to be spending in the grand scheme of things. The blue book sale value of my car is 27k, with a trade in value of 25k, and the g35 has a sticker price of 38k. Obviously it will be 13k over what I owe on the TL which I'm guesstimating at 15k, but then how much in extra value in the car am I gaining?