Ron-
Stock agencies - oh boy. I think they are generally idiots when it comes to image quality. Unless something has changed recently, they base all of their standards on film scan information from 10 years ago. And those standards don't really apply to digital images. If you want to sell through them, you've got to follow their rules, of course. But please don't consider them experts, by any means. They've got their own best interests and convenience in mind, not yours.

For color management, I don't know if the ColorMunki is the best product out there. Our reviewer had some real issues with it. I've been using the Spyder for years - I think I've used every version of it. And it's always worked well for me. The software can be a little clunky, but I've found that to be true for all color management software. But ultimately it does a good job of calibrating your monitor. I've also used older X-Rite monitor calibration hardware and it's worked well for me, too. Basically, just get something and use it. No matter what system you use, if you calibrate with monitor calibration hardware, you're going to improve your color and the ultimate quality of all your photos. We actually have a color management review section, although not very many people have posted reviews. But here it is:

Color Management Reviews >>