Strong wheels
So, touring on a road bike eh?
If you're not going to put much weight on the front wheel, you might not need a stronger front wheel. Of course, trailer or panniers, the rear wheel is critical. The Mavic A319 and A719 are very strong touring rims, but the CR-18 is strong too - and as you said, quite affordable as it has been in production for so long, in such large quantities. No wonder the CR-18 is so popular - strong and cheap.
Of course, wheel build quality is more important than which touring rim you use. A well-built wheel with high quality spokes, equally and properly tensioned on each side, stress-relieved and detwisted, will be stronger than a poor machine-built wheel, regardless of the rim.
My touring rear wheel is an A319/DT/Deore 36 spoke wheel, and it works great with a 28mm Marathon Plus.