When considering any type of high-loft insulating jacket (whether down or synthetic), it's useful to remember that these pieces often don't layer well under shells.
The problem is that the weight of the shell can often compress the insulation, significantly reducing its ability to keep you warm. This is particularly true of the shoulder area where the insulation is often most critical for warmth but which tends to be compressed the most, especially with hands stuffed into the shell's side pockets.
Perhaps ironically, this issue can be most pronounced with the kinds of high-end, super-lofty products that lightweight backpackers tend to seek out since the ultra-puffy insulations (like 800+ fill down, for example) tend to compress more easily than some lower quality insulators.
There was an interesting thread recently about this issue over at TLB.
Creates kind of a dilemma. On the one hand, a shell (which you're already carrying) can, by itself, offer several degrees of warmth, but on the other hand, if you wear that shell over a lofty insulation piece, you're probably going to lose a fair amount of warmth from compression.
So another option I've been using for the past couple of years is the (relatively) new Polartec Thermal Pro fleece that's lighter, warmer and more compressible than the classic stuff. Specifically, I now mostly use the Mountain Hardwear Monkey Man jacket that weighs about a pound in size large. Super-durable, very warm (especially when layered under a shell), quick to dry, and highly resistant to damage from stuffing, it might be a choice you'd like to consider.