looking sheldon's gear inch calculator you went from 64 gear inches to 72 which is a good ideal range for single speed bikes. I did the exact same thing to my Tern dropping out the 17t cog to 15t and gained around the same but changing out my tires from the citizens to a pair of kojaks. Oh boy do those babies roll fast!

at least with this new setup you can take your time and decide on whether you really need a two speed hub. The ONLY choice you really have is the sram automatix or if you can find some old torpedo hub from another vintage bike. The sturmey archer s2c mostly have problems for alot of users and some of them just locked up the wheel after the insides when kaput in short distances! If automatix isn't your thing then a 3 speed hub would be more durable from any of the big manufacturers (sram, shimano, sturmey)