I know the following combination is not the ideal for ultralight backpacking but I got them all at great sale prices. My question is: at what temperature do you think this system will keep the average person warm to?

Mid weight capilene shirt
Marmot Driclime
Patagonia Micro Puff Pullover
Marmot Precip

Assuming reasonable protection for head and lower body... I would expect most people would be comfortable to sub-0F temps with all layers on.

I run warm. Provided I have had enough food to eat and am not exhausted, the Microsoft Puff Pullover + midweight base would keep me warm to ~15F sitting around.... and when active I was comfortable to -15F (that's the coldest it's gotten when I have used the Micro Puff.

The US Army insulation recommendations would suggest that the Micro Puff by itself (.7in of loft) would be comfortable for sleeping to 50F, awake and light activity down to around 40F, and if enaged in high energy activity to below -50F.

Those tops, matched with suitable bottoms, could easily see me into the teens Fahrenheit, just piddling around. If active, then probably much lower. Unfortunately, I can't really tell you much more because it rarely gets that cold in Georgia :)
-Mark

I use a similar setup for upper and lower layers:
Patagonia midweight Capilene
Patagonia Micro Puff Vest
Marmot Precip for rain/wind protection
Mountain Hardware windshirt
combined with gloves and a balaclava I can handle about any weather I encounter..

Of course I mostly hike in Georgia and sometimes venture into North Carolina so I do not have to deal with extreme cold either.