Aaron, unfortunately, everything is a compromise. However you made three very good choices. Here is my take.
The best bang for the buck is the REI Rondonee. It is on sale until 4/18. As you know, normally $1049 now $799. It even comes with a rear rack. (they honor rain checks, if out of stock) I like STI's but there are those who prefer bar end shifters. I know someone who put both on. (not as crazy as you think) You can get bar cons for little money. I would run the STI's on your 10 day tours. If you are going to remote places, switch the cable routing to the bar cons. (or you could have them switch them when you make the purchase an maybe save some money.)
The compromises with the Rondonee based on your criterias:
1. Wheels, I believe they only come in 700X32 wheels/tires. Your will want fenders. You should carefully look at the tire clearance. If you could go up to 37c you might be able to get by, unless the terrain is really marginal. (unfortunately with fenders you may have to go down from a 700X32 to a 700X28.)
2. Looking at 2010 specs, I question their choice of the drive train they provide. 30-39-50 crank, with a 11-28 rear cassette is a little high for me. (29.4" low gear & 125" high gear) I believed they had offered a 26-36-48. *I will included, at the end, an excerpt from a person who recently purchased a 2010 Rondonee, in Washington State. His comments may get you the bike a little more custom for very little money. (From an aesthetics standpoint, I like the new color.)
The Surly is a very good choice and in your 54c frame size, as previously mentioned, it will be a 26" tires. It is pretty much outfitted the way you want. (I like the spoke holder, nice touch) However, it is $186 more than the Rondonee. (I believe all three bikes basically have Reynolds 520 tubing)
*Comments about Novara Randonee Touring Bike - 2010:
"What a great bicycle for the price. Love the new color for 2010! I had REI swap out the RD and Cassette to more proper gearing for touring. Total cost of changes was close to $5 total. Had them install a Deore XT Long cage RD and also an 11/34 Cassette. With those changes I have nothing much to complain about. I prefer STI shifters but I suppose if you don't, you could swap them out for bar ends at time of purchase as well. This would only make the purchase less. Rei does retail for retail swaps with free labor at time of purchase. I measured the chainstays myself and they are approx 460mm. That is a sweet length for touring with larger panniers and big feet."
If I may, I have one other suggestion that you did not mention. I know how you feel about steel, steel is real, but there is an aluminum bike, that might fit all your other requirements. The REI Safari. If you can fit a medium frame, it comes with 26X1.75 tires. If you go to a large frame then it is a 29er. 700X48! The gearing is 26-36-48 crank and 11-34 rear cassette which translates into a 20" low gear 113" high gear.(26" wheel) I rode a Cannondale aluminum bike for years and with the cushy tires, on the Safari, if you add a seat post shock, I think the difference, in comfort, would be minimal. I like the geometry better, on the Safari and I think the fit may be better for your torso/arm measurements. It comes with Disk Brakes and a good rear rack. It is also more robust and would fit your South America requirements. Because it is aluminum, you may not suffer a weight penalty. I can not speak about the shifters. The best part about this bike is normally $849.00 and is now on sale for $679.20.** Think of all the accessories you could purchase with the difference. **If you are not a member, $20.00 and print the coupon out online. Sales ends 4/18.
The bottom line is, if you go in with an open mind, you will be able to ride both REI bikes, providing there is one near you. (I am not sure if you will be able to fine a Surly or Trek to ride.) If you purchase a bike from REI, they are a very good outfit, and if you don't like the bike, you could return it, for a full refund. Good luck in your research and let us know what you decide