Choice of new crank

My new bike is on the way to me as I type and I know the weakest part of it already is going to be upgraded very soon.
Cervelo P2C - The crank has to be one of the areas I want to upgrade right off the bat (have not had good luck with FSA in the past)

I know the Bottom Bracket on the FSA Gossamer is an external as I just replaced the one on my wifes QR. I really wish this would have been made an Ultegra SL crank, but that just adds cost.

My question would be:
1 - Is there any benefit to swapping out my Shimano 105 Crankset/BB from my Trek Equinox with the FSA setup that comes on the P2C Ultegra SL package or are they similar enough to not be worth the effort?
2 - I figure upgrading to the Ultegra SL crank is a no brainer outside of the cost factor, but was not sure what would be a better decision, using the 105 setup if they are even compatible, the FSA setup for the time being to get by until I pick up the SL crank.

I guess finally are the higher models of FSA cranks any better, looking at the carbon models? I have always felt like the Gossamer is noisy and clunky.