Eurgh. So you may as well buy the CX50. It's basically a fc-5750/fc-r460 crankset with appropriate chainrings already. You may want to pop a 34T in there instead, but those are easy enough to find. The fc-r460 and fc-3550 can actually be found with a 46-34 set already.
Need 4 arm for new fangled Shimano