I was able to find the measurements from the old Trek Catalog:

Seat tube length 41.7 (old bike: 47.5)
Top tube length 54 (53.6)

He lists a measurement of 28.5 for SO height, and my current bike is just under 29.5.

So, it really does look like the big difference is the seat tube/size ... a bit confused on the sizing still, unfortunately I can't go check it out in person.

(Seat tube angle and head tube angle are 73 and 70.5, compared to 73.5 and 72)