I can't speak for the Madone but I have a Lexa SLX (the top Lexa model) and I love it. I used to have a full carbon bike before I bought this one and I honestly can't feel a difference at all. If you can swing the money for the Madone then go ahead and get but don't feel like you are getting a bad bike if you get the Lexa. Also, not all the Lexas are triples; mine isn't.
"What am I on? I'm on my bike, busting my *** 6 hours a day. What are you on?" Lance Armstrong
2011 Quintana Roo Dulce
2011 Trek Lexa SLX