What are your current numbers and where will you ride? How heavily will you be loaded?
The cheapest and easiest change is usually to just change the inner chain ring.
I find a 24t inner chain ring and 32t sprocket about ideal for me. That said, I rode across the US with a low of 26 front 32 rear and found it adequate. I only wished for lower a couple times in the Appalachians and never in the Cascades or Rockies.
BTW: That is a great looking bike.