You can just change your big ring from 50 to 46. You may need to get another FD after if shifting start to suffer but I usually don't bother unless I have CX specific FD handy (I use shimano and cx50 FD was designed to work with smaller chainrings)
FSA will be making 48/32T, 46/36T, 46/30T soon, FSA Omega MegaExo - Full Speed Ahead. If you decide to change entire crankset - makes sure you get appropriate BB.


Another option is to change cassette but again you may need another RD