I've finally figured something out with my scanner and the software I'm using. Utilizing an IT-8 calibration target card (in which I'll also have at least one Kodachrome slide around forever), I got the scanner's profile set correctly in the software (Vue Scan). Then choosing the profile for my film (which I was already doing, but without the scanner's calibration) I'm getting not just real colors but accurate tones and shadows. Nice!
Now I'll just have to re-scan several rolls of film from the past year, so that I can assemble this year's photo book of the kids for the grandparents and aunts.