It sounds like you have it somewhat narrowed down to a few good options, and as Brad mentioned the "best" boot is the one that fits properly! In terms of insulation, not all insulators are created equal. Boots like the Lowa Sheephunter and Schnee's Granite are using PrimaLoft insulation (200 Grams). IMO PrimaLoft is about as good as it gets for warmth: it has a higher warmth to weight ration than thinsulate or other synthetics (200 gms of PL would be about equal to 400gms of thinsulate), and it much more effective at moving moisture and maintains its insulating ability when wet (thinsulate loses r-value with saturation)!
