Why not just buy a nice 105 carbon now, if you're SURE you'll want it in 6 months?

Go to your LBS, get fitted and get a "real" bike. Even though you're getting a "good deal" from BD, a properly fitted bike and a LBS that will assemble it and make the fine adjustments you're going to need in the first few weeks.

I just picked up a full 105 aluminum 2011 Trek for an insane price, and I love it. I rode a 4.5, and didn't think spending more than double was worth it right now to save 2lbs. I will use this one for a year or two, then get a serious carbon with dura-ace, and use this one as the commuter.