Russ, touched a nerve did I...
We all have to decide about what is important to us. I will admit that I am a big fan of using mountain bike cranks on touring bikes. At some point in you life, having that enhanced low end is nice when you are humping your stuff up a grade.
The OP (original poster) complained about the total range available on his current crank, not just the low end but the high end too. Yes you can swap out rings (except when Shimano rivets them on). The ramps and pins do improve shifting, but they also elevate the cost of the replacement rings. I would still pay ~$100 for a high value mountain bike crank in the desired range than ~$70 for economy chain rings to convert the existing Sora crank to that same range. Better shifting is worth ~$30 to me. But every else is entitled to their opinion.
I once had a Tiagra triple which I think was a 30/40/50. I did swap out the 30 and put a 26 ring in its place. The dealer could only get a 26 ring, and I never checked to see if there were other choices. As I recall, the shifting was not too bad, even with Tiagra brifters, but I ultimately wanted a little more on the low end and put an LX mountain crank in its place. When I sold the bike I put the Tiagra crank back.
The right crank for the OP is the one that meets his needs. I don't know that the Sugino touring crank would be my first choice in an after market crank. There is nothing wrong with Sugino or tapered square bottom brackets, but Shimano still calls the shots in the bicycle component world. About 15 years ago Shimano started the transition from tapered square bottom brackets. Right now Shimano pushes the outboard bearing cranksets. At some point, sources for quality tapered square BBs are going to dry up. There are lots of sources for new outboard bearing cranks besides Shimano. As far as I know, all of the outboard bearings are interchangeable, so a new crank could mean useful spare parts.
Either way, swapping rings or another outboard bearing crank really is something that even an novice can do. And maybe just trying out a new little chain ring is worthwhile since the out of pocket cost is so low.
One final caution, going from 32/42/52 down to 26/36/46 (or lower) may also require a new front derailleur. You will not know until after the swap. Good news is that front derailleurs are pretty cheap.