Well, after much market research (thank goodness knitters love to share their experiences) I have been assured that Misti Alpaca's Hand paint Pima silk and Misti Alpaca's Tonas Pima Silk Yarn are both excellent choices for a cardigan. This by knitters who have knit cardigans with these yarns, worn them, washed them, worn them again. I looked at people who had completed projects from at least a year ago. It takes time to know if a yarn will stand up and it is reported that these two do just that.
One knitter said there was a small amount of growth after several days of wearing but that the cotton shrunk up nicely again in the wash. This I can live with.
But, I'm getting ahead of myself. After I finished the Cowl Shell I got hunting for patterns for a cardigan to layer overtop of it (more on that later) and then that led me to hunting for a DK yarn that would have some multi-tone or variegated color with just a hint of the Blue Pine tone from the cowl.
A few people on a Ravelry forum suggested the Misti Alpaca yarns and so I took a peek at the color possibilities.
1. Misti Alpaca's Hand Paint Pima Silk yarn is a soft, DK weight yarn of high quality Peruvian Pima Cotton blended with silk. Our Pima Silk Hand Paint is a unique technique resulting in subtle blending of many many colors per hank. 83% Peruvian Pima Cotton/17% Silk
The color I chose is Jardin. It has all the colors from my color palette in here. I think I really love it and I think it would go great with the blue pine hempathy, don't you?

I was all ready to proceed to check out when I decided to just have a quick look at the other suggested yarn:
Tonos Pima Silk DK: The perfect blend of Pima Cotton and Silk in a DK weight. This collection is designed with a tone on tone hand paint technique. 83% Peruvian Pima Cotton/17% Silk
Bahamas is such a perfect color and so well named.

Sigh! Do you see the blue pine in there? Plus all the lovely teals and greens?
So what should I do? Which color would you choose to pair with this?

Please vote 1 or 2 in the comments and feel free to expound on the reason for your choice!