I have not yet found a build order where it's best to build a reactor first. And if the best he has is Warthogs with just gunner then the turret(s) you should already have up will be able to deal with him. Gunner Warthogs are nothing more then just an annoyance. Easily countered.

Bura1987:Having recently played a few games against the world number 3 Toyo, I am wondering whether his reactor first build is worth it. What he generally does is goes reactor first, gets gunner and is at your base within the first minute of the game. He tries very hard to take out an early warthog then focuses on buildings being built. Do you guys reckon this is a viable tactic as Anders as I usually go supply pad then reactor???