Me and wife had back pain issues due to long hours of sitting in desk job. When we started searching for mattress, i found that people spend insane amount for those feather touch feel and Sales people would say a lot of stories like - you spent 1/3 of your life, sleep is important, back is important.
Long story short, after trying many we found that none of memory foam or the fancy stuff is not required or going to help us.
We went with firm foam mattress from Ikea (i think it was around $500). Now they deliver, so you dont need to worry about transportation. I carried the rolled mattress in my Prius, it wasnt weighing ton when it was rolled.
Buying online - 50/50 of like/dislike. I got a firm memory foam mattress from wally for our guest room. Its good, but we agreed that our king size foam bed is firmer than this one which we liked.