I own the "Comp" version of this bike which has the same frame and many components, except a different groupset (Tiagra vs 105) and brakes (TRP Hy-RD vs Shimano full hydraulic). Also this has thru axles. I've seen this bike on sale at Nashbar.com in the $1200 range but MSRP is $2000. It's a heavy aluminum frame but as long as you're not racing cyclocross, the bike gives a very comfortable ride.
The Expert adds the Shimano 105 groupset, hydraulic disk brakes and thru axles. The other sizes are over twice the cost. Looks like only one is available. If it was in size 58 I would buy it on principle. Size 56 should fit 5'10"-6'0" people, but it depends.