Sweet spot on road bikes is around $3K. That'll get you a very good carbon frameset, groovy wheels, and a Ultegra gruppo. This is what 98% of us need and if you are in the 2% that could tell the difference, you wouldn't be asking the question. Don't squander thousands on a bike that you can't tell the difference on. Any less than around $3K there will be some compromises, much more than $3K is just spending.

And buying it piecemeal just increases the price overall.

Wait, if you can, until the fall, when the 2010's are being sold off cheaper. That's the time to buy. Walk in w/cash, check out the Ultegra level offerings, you'd be amazed at what you can get.