Nuns assessment works great for his setup, a light bike, a very light load. His view on the range of gear inches is very realistic, but again, depends on the load and the terrain.

For me the kicker is what sort of load do you think you will be carrying, but even then I am very much a fan of triples. FDs shift perfectly well with triples, and the angle of the chain is always going to be better, guys in stores dont give a hoot often about cross chaining and such, and also will tell you that you need to change your chain every 1500km or whatever--and I may be an old sourpuss but usually folks who give out gearing advice in stores havent toured with lots of weight in hilly terrain.

Plus in my experience most of the time we are in the middle chainring, so it reduces the amount of chainring shifting one does. I too like tighter jumps between cogs, and a triple will help with that as you can put a tighter cassette on and still have the triple range of gearing from up front. In fact, tighter jumps and closer jumps between chainrings is even more important when you have 30, 40, 50 lbs of crap on a bike as it is much harder on the knees and legs with bigger jumps between shifts.

my take on ideal cranks for a touring bike--for most touring situations and the bike being used lightly or unloaded, 46/36/26 works great.
A mountain crank 44/32/22 can also work great if you are fully loaded and or will be in really mountainous terrain--people poo-poo this gearing but the reality of heavy touring is that you will most often be riding from 10-25kph, and a mtn crank works fine and can give you lower gearing below 20 gear inches easily for really steep hills.

Give us an idea of what touring you have done, with what sort of weight and in what sort of terrain. As mentioned, this will really give a better idea of what sort of situation you will be touring in the future--is it a 20lb bike with 15lbs of stuff riding in Florida, or a 35lb bike with 50lbs of stuff in the Alps or the Appalachians.

ps, 8 speed stuff is cheap, 9 speed stuff is now nothing special so reasonably priced, 10 speed stuff much more expensive (chains, cassettes) so perhaps look into the prices between 9 and 10 stuff. Also to consider that 10 speed stuff would be harder to find parts depending on where you are planning to tour. I only know 7, 8 and 9 speed stuff for longevity so can't speak for 10.
Id go with 9, just because its still got slightly closer gearing jumps than the equivelent 8, but has been around now for so long that finding parts as mentioned is easier and cheaper (again, not an issue if in N American, Europe) and seems to me to be the good balance of cost/performance.