I'd highly suggest renting a variety of bikes, testing them out, then buying those that you prefer.

I'm 5'11" with a 32" inseam. I also was told that a 56 would be the best for me. I rented a 56 Roubaix, which was ok. The next week I rented a Tarmac, the shop didn't have a 56 so I got a 58 (they had 54 or 58 for rentals). Turns out that the 58 Tarmac was perfect for me, and I bought one.

Even if the size is off a bit, a good fitting may be able to correct it, maybe not. My Tarmac was just ok until after my fitting.