mrbump, I’m 5’11” but with long legs, short torso ( crushed vertebrae, used to be 6’0″!!), so according to Cy a medium with a long seatpost was the way to go. He’s right.
At 5’8″ I reckon a 16 would be perfect. Your build looks great.
Try Cycle-Fast.co.uk , he had some bargain flow rims in recently, and will do coloured hubs, not just Hope Hoops black.
If you want to go AM, then I’d say Flow. Take a wider tyre. I ran Arch EX with 2.4 nics and they were pretty much on the edge. They’re much happier with 2.25 now.