For me, staying warm and comfortable and carrying lightweight stuff involves two items. The first consideration and first purchase for me was to buy a good air filled mattress, in my case a Thermarest Neo Air. I then decided that I would not buy a sleeping bag again. I chose to buy a down sleeping quilt (Rule 1, never get it wet!) which has no back and no hood. I'm very happy that for once in my hiking 'career' I made two good and intergrated decisions. Previously I had a sleeping bag and a mattress which in those days I just bought as separate items. At some point a few years ago my brain told me that to work well, each item needed to be complimentary to each other and work as a single unit. I then realised I had solved my sleeping problem! For me, my quilt and NeoAir are almost perfect in the warmer months. When its colder I just wear long johns, occasionally a thin pair of loose socks, a long sleeved tee shirt and sometimes my warm jacket (not down) as well. Mostly, rather than wearing it I just throw it over the top of my quilt, I've never really worked out which works best for warmth, to wear it, or not to wear it overnight? My experience is that if I've worn the jacket all night and then get out of my tent I don't feel warmer, if I throw it over me and then put it on, I believe I do feel warmer. I've no idea why? If I wear it all night, perhaps its the residue condensation in the jacket fibres perhaps that keep me feeling cold?