Last year, I was in your position looking for a mattress. As an alternative, I looked at AEROBED air mattresses. Made by Coleman.
Used it on a 115 night trip. It is the most comfortable mattress I have ever slept on. Comes with a built in air pump. The main thing you have to remember is to partially deflate if you are going into the mountains. The lower air pressure causes the air inside to expand--bang. They weigh 30 or so pounds and mine came shipped for about $100.
One negative--One of the interior supports broke after the trip and it developed a bulge. It was still usable, however. I wrote AEROBED and sent pictures. It was under warrantee and I got a new one in 10 days.