The top quilt worked fantastically, with no need to supplement.
A 3oz climashield quilt by itself should be good to 45-50*. More if you use proper clothing.
Here are a few pics. The IX overcover is basically the same design as the quilt, made just slightly smaller (causes the quilt to go into a "forced fluff"). IX overcover has two layers of insultex (IX). Overcover can be snapped to the quilt, along the edges.
TQ-IX 6.jpg TQ-IX 4.jpg
This thread discusses it extensively.