I'm all for supporting the bike shop, and regard AEBike as a good one (I've ordered from them before as well) but still, I say build your own wheel. It's fun. It's easy. It's... well, I don't know, I just like to build all my own wheels.

I did find that hub a bit cheaper; on a purchase of that magnitude I will use Google Shopping to find the lowest price / shipping, always bearing in mind that if I can get everything from one shop, the reduced shipping will often make up the difference in price.

You don't really need the tensiometer. I built dozens of wheels before I got mine. I did eventually get one, however, because I'd built a wheel that ate spokes like potato chips.

At any rate, regardless how who and how much, go for it! You're going to love the hub, just be sure to gear it low enough, like a 38T / 19T combination should be pretty good.