"Cheap carbon" is perfectly fine. The whole idea that an inexpensive aluminum frame is way better than an inexpensive carbon frame is baloney, IMHO.

If you can afford it, the Trek Emonda S5 with 105 groupset looks like a nice bike. If money is an issue, the S4 will be just about as good except it's 10 speed instead of 11 speed. Tiagra 10 speed works great, I bought my gf a bike with it and when I assembled it and test rode it, I was impressed with the quality. Other than the 105 vs Tiagra drivetrain, all the other parts between the S5 and S4 are listed as identical on Trek's website.

If money is no object, then why not get the SL5, sure. But remember that you will want to set aside some money for pedals, shoes, clothing, water bottles/cages, flat repair stuff, chain lube, floor pump, minipump, etc. You can really skip all that stuff except for the flat repair, chain lube, floor pump and minipump but that's still at least around $50-100 more that you will need to spend beyond the bike.