I own and ride a Surly Cross Check and a Trek 520. The Trek 520 is a great touring bike when fully loaded.
My Surly is setup as a fixed-gear and it's a wonderful bike to ride. I haven't toured on it yet unfortunately.
When riding the Trek 520 unloaded after riding the Surly the Trek feels like the tires are flat, steering is sluggish and is in general not so much fun to ride. Having said that the Trek 520 also seems to feel different when loaded up almost like it needs to be loaded to feel complete.
I don't know how well the Surly will handle weight. It is a fun bike to ride, works well on and offroad and has a charm that calls out to you and seduces you into riding it all the time.
I haven't ridden a Steamroller yet. I imagine that it shares some characteristics with the Trek 520 since they are both designed for similar purposes.
For everything but loaded touring I can easily recommend the Surly Cross Check. I haven't tried loaded touring with it yet so I can't comment on that aspect beyond what I've already said. I am concerned that the frame might be twitchier under load and if you are touring long distances on a daily basis this might take more of your energy then you would like.
~Jamie N
www.bicycletouring101.com