I've found a sleeping bag in the 25-30 F range works good in most situations. I believe that it is easier to cool off with a warm bag than it is to get warm with an inadequate bag. I also prefer a synthetic bag because it can be machine washed and quicklydried, and is still warm when wet. Check REI and Campmor for an idea of what is available. A 25-35 degree rated bag can be found that weighs 2-3 lbs.

A Thermrest Pro Lite 4 makes a good multi-season sleeping pad.

I also think a good nights sleep is worth carrying a little extra weight, especially on a long tour. My wife cut made some pillow cases to fit our stuffable pillows. This keeps the pillow clean and the cases are easy to clean.

Our bags are Marmot are "Pounder Plus" 25 degree, synthetic bags weighing a hair over 2 pounds. Unfortunately, they are no longer made.

On short summer tours we sometimes take 45 F rated bags, but have spent some uncomfortable nights, even in summer. On a tour late this summer we experienced temperatures in the low 30's which was a little cool even for our heavier bags.