Get this nemesis sport. Do raceface aluminum cranks, raceface narrow/wide ring, x9 type 2 rear derailleur, light bars/stem/post, carbon tapered fork, xo gripshift, crest wheels. Be $1500, superlight.
You can talk all you want about the weight, rolling resistance, acceleration....but the 650b just feels right. If you put a 650b with 2.1" tire next to you 700c wheel with tire, it's about the same. It makes 29er bikes feel over bearing, fat, and stupid.