I don't usually get into the this model or that model specifics, but this time I got curious. The first three are pretty similar, while the Liv looks like the "shrink it and pink it" version of the Revolt. All four have low gears of about 27 gear inches. Russ's bike has been modified to about 24 gear inch low, and I'm not sure what Pete's low gear is. My preference is to go lower, to 22 or even 20 gear inches, and I've used those after 50 miles of hills when there's another 10 miles (and one more mountain!) to get to camp and my gear. Ergo, I'd recommend you discuss the possibilities for lowering gears with the bike shop before you buy. Ask about subbing in a mountain double crank, or a triple, for the stock gearing.
- Liv Brava SLR Cyclocross
- Giant Revolt 1
- Specialization Dolce EVO
- Surly Straggler
Could they handle racks and bags or it's not recommended?
The Straggler leads the way with eyelets for racks; I didn't see anything that looked like an eyelet on either of the other three, so you'd have to go with clamp-on rack mounts or Old Man Mountain racks.
It looks like all the models you're looking at have reasonably fat tires. Get the bike now and wear out the tires by next spring, so you can put on some nice, light, flexible slicks before you leave. (If you get the Surly, swap them out now and save the knobbies for trail rides.)
Above all, go down to your local bike shop and start test riding! For a light, credit-card touring load, you shouldn't change the ride too much. Pick the bike you like to ride, from the dealer who will fit the bike to you, and the dealer that everybody likes to go to for after the sale service.