Although your questioning may be to get at the basic underlying theory, think more in terms of real-world situation. You are never going to fly at sea level, so let's say you want a "low level flight" of between 1000-2000 feet.
25/2500 would give you 975 in range and about 184 knots
25/2100. 1175. 161
Now climb to 10000 feet at the same power settings and you see
25/2500. 1100. 194
25/2100. 1270. 170
So the old axiom is true, that as you climb, you will gain range and speed. Looking at the lowest possible power setting and the lowest altitude (flying in ground effect(!)) you could increase you total range (but at huge huge cost in relative time and comfort. Stuck over the ocean in a 0 wind situation, it might some day pay off to be there.
In the real world, consider a 1000nm trip in your Baron. At highest possible power, 5.1 hours, at a moderate normal cruise 5.4 hours and at low-level 7 hours.
Go to your fuel flow table and compare the fuel burns.
Probably clear why normal cruise is normal...normal meaning most totally efficient. And at these power settings, climbing does indeed give you better range and greater speed RELATIVE to the same power at a lower altitude, except for a very small range at the lowest end of the table, which is not often a good place to be for other reasons in the real world....
IMHO