In reply to Vonduffer:
I would be inclined to go for the PipeDream 600 over the SkyeHigh 900 - lighter, packs smaller, and has the same temperature rating near enough.
As for the Bivi bag - no need if, as you said, you'll be in a tent.
Not tried the Thermarest and I don't use sleeping bag liners as it's extra weight to carry all day for a bit of luxury in my opinion.