I have a BA Lost Ranger and 2 different pads to go with it. One is a self inflater and the other is a blow up insulated. If I recall the blow up is rated to 15 deg (same as the bag) and the self inflater is good down to 0 deg. I slept with the 15 deg down to 32 and was more than toasty. I have the long version of the bag so it's plenty roomy for any sleeping position, at least for a person of 5'10" stature and on the wrong side of 200 lbs. I know all the gram weenies ( ) will say it weighs too much but I have my own views on packing light and for me it fits right in. The system as is will keep me plenty warn down to any temp I'm likely to hang at and if I get a wild hair and really want to go cold I can always add a Yampa overbag.
I'm not a big fan of the over-quilt under-quilt systems since to me they are too expensive for what they are and too specialized. I can use my bags/pads anywhere and everywhere and all of them together cost less than a lot of the over-quilts, let alone an over under combo.
I tried the standard bag/pad combo and keeping everything where it needed to be made for a poor nights sleep at best. I'm pretty happy with the BA system.