My levels are perhaps not as refined as yours - but run something like the following. I used to live in western Wisconsin with no household car, so the levels needed to cover down to around -15F. Over around 45F, I get away with normal cycling gear, like fingerless gloves, knee warmers, sleeves, and a wind jacket. Then the fun starts:

Level 1 (low 40s to low 30s): Wind jacket with wool baselayer. Tights, full-finger gloves, thin wool socks with booties, ear covering, sunglasses.
Level 2: (low 30s to low 20s): Vented softshell with wool baselayer. Thick wool socks with booties, add silk liner to full-finger gloves, add balaclava.
Level 3: (low 20s to maybe 10 above): Vented softshell with thicker wool baselayer. Thick wool socks with booties and toe warmers OR winter boots, heavy GoreTex ski gloves, add snowboard helmet and ski goggles.
Level 4: (10-0): Vented softshell with multiple wool baselayers. Winter boots, add single liner to ski gloves, add outer layer (rain pants) over tights.
Level 5: (below 0): Vented softshell with multiple wool baselayers. Winter boots, two liners in ski gloves, outer layer (rain pants) over tights, additional face cover. In western Wisconsin this kind of temperature usually means high winds, so the idea is to eliminate skin exposure.

I've heard that as well. Fortunately, my workplace is pretty good about shutting down for inclement weather, so I should not need to commute much, if at all, on the ice. I brought the studded tires just in case, because I've been commuting for so long that my winter driving skills are pretty much nonexistent!