I have swapped components to different frames many, many times. Actually, my bike shops have done it, and it generally costs about $100-150 labor, depending on how much time it takes. I usually end up having to buy a few different components, which adds to the cost. I would check with your bike shop, unless you plan to do the work yourself. If you order the Soma frame through your LBS, they might give you a break on parts and/or labor.

I actually had such a frame swap done with my touring bike last fall, moving parts from my Bob Jackson World Tour to a new Soma Saga frame. I had to buy a new stem, headset and rear wheel but everything else fit fine.