I just purchased my first Hammock a couple months ago, and have been trying to get out camping as much as possible. However, its getting colder here in Maine, and I am still waiting to get cold in my hammock.
I do not have a tarp. I do not have quilts.
All I use is a Therma-rest mat between the layers of my WBBB DBL 1.7, and a USMC modular sleep system with goretex bivy. I have camped as low as 17 F, and wake-up uncomfortably warm, though not sweating.
The upside to the modular sleep system is of course that it is modular. You can use different sleep bag combinations based on the conditions. Secondly is price (compared to purchasing more than one sleeping bag...or quilt(s)).
The modular system when combined is waterproof and rated at -40 F. The two individual bags are rated above 30 F, and 10-30 F. When I do not use the combined system, I use the extra sleeping bag as padding/insulation beneath me.
The downside is the size and weight, though I do not know the difference in weight versus carrying a top-quilt and under-quilt. The complete modular sleep system in the compression sack is 8-10 lbs.
I am hoping to get down to 10 F with this set-up, but am not holding my breath. I should also add that I have been fortunate not to have encountered high wind (so I just picked up a Superfly).