I'm not advocating your bike buying decisions based on someone else, but since you already purchased the bike and would like some approval of your decision - I am 5'10" - 5'11", and also buy 32 in. inseam pants, and I ride a 54cm Cervelo One. I am not sure how many spacers I have below my stem, but I do know that this size bike is maybe a tad big for me (I'm on a 90mm stem).

Don't worry about the QR being a 57cm, they don't measure their frames the same way as Cervelo, and QR's top tubes tend to run small for their listed sizes anyways. Sounds to me like you are pretty close to the right size bike (based on my completely unqualified opinion). If anything, I've been told by respected bike shop guys that it's way better to be on a bike too small, than one too big.

Enjoy the new ride, I love my One and those P2K's sound like an upgrade in all the right places.

--------I originally posted this before I realized there were replies above. I guess this shows you why going by height and what length pants you buy is not the way to buy a bike. I say, if you trust the LBS, then they probably put you on the right bike. If your worried about it, post your picture on here and see what some of the people say about your position.---------

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."