The Praxis have a 110BCD, so in theory you should be able to use other chainring, however I do recommend sticking to Praxis' own, as they work really well and a worthy alternative to Shimano offering (especially since they come down to 48/32 using their chainring and bolt).
Agree, I'm now on 46/30 with a 14-28 block, right now the 46t is being use all the time, and the 30t is for the mountain/audax/etc.