True, there are a lot of subvariations. Not all of them are ridiculous: there are some laughable ones as well.
That 6.Qa4 is a terrific idea. How many hours your Houdini thought before suggesting that?
Quiet moves don't seem to give Black any problems e.g. 6.Bg5 Bg7 7.Qd2 d6 or 6.Bf4 d6 or 6.g3 Bg7 7.Bg2 Nc6
Black can refrain from committing his central pawns and get a good game. While not conclusive Houdini 3 played aggressively against this plan and Black had good equalizing resources:
1.c4 c5 2.Nf3 f5! 3.Nc3 Nf6 4.d4 cxd4 5.Nxd4 g6 6.Qa4 Nc6 7.Ndb5 a6 8.Nd5 Kf7!
Obviously there are a lot of subvariations, but in none of them does White barely get to +/=.