It depends on what you want to do with your bike. I swapped my 46/36 to a 48/34 to give me a higher end while also providing some good gearing for the hills we have here in the North East. In both cases, I used the 11/28 Cassette. I ran it this way for two years - and here's my verdict: first - it sucked for racing - so if that's your intention stick with the 46/36. It was great on the road and in group rides - however, I recently switched back to the 46/36 (I got the Cx70 by Shimano to be exact). The reason was that most of the time - the 48 was a bit too high of a gear for normal riding (plus it sucked on trails). with the 46/36 - I can ride in the larger crank a lot more and the 36 seems about right for all but the steepest hills. When I need to replace my rear derailleur - I will probably opt for a medium cage to allow for a 12/30 or 32 rear cassette which will be plenty for the hills.
Overall - the jump from a 34 to a 50 is quite a lot - so you shifting might be an issue. If you wanted to change things, I would go with a 48/34. I used FSA cranks and chainrings and shifting was flawless.
As I mentioned - unless you are doing some serious group rides - I think the 50/34 would limit your overall usability for your Cross bike.