The SWFA glass is a great bang for the buck, My 308 at the moment has a Premier 5-25x that cost as much as the rifle. I have been drooling over a new S&B 5-25x tan but find it hard to spend $3500+ on glass at the moment. (if they still had the Gen II reticles I would probably already own it).

If you can not get the glass you want now because of funds, I would hold off as long as possible and see if you can get what you want by the time the rifle is built. No matter how good of a rifle it is, if you can't see what you want to hit its not going to matter.