Just based on my own preferences, 46x15 is too much. What you have now is a fine gear, a 46x16 cog is about as high I like to go. I would stick with the current gear and put the 15 or 16 on the other side of the hub, if the hub is fix/fix.
I run 48x19 with an 18 on the other side. Occasionally I'll ride the 18 for the hell of it and for fast group rides so I have slightly a higher top speed.