Pads Pain

What english saddle pad is best to relieve back pain?

My horse has been very sore-backed lately, and I'm pretty sure it's because of my saddle. I am getting ready to buy a new one, but I also want to buy a saddle pad that can help prevent back pain. What is the best kind (gel, sheepskin, foam, etc.) and what is the best brand? Thanks!
The three main ones that I am looking at are the Wintec Gel Comfort pad, the Traumatech pad, and the Equine Comfort Sheepskin pad with Gel Inserts.

Gel Pads are really good, but if it is just the clear gel plastic you need to put it inside of a real saddle pad-- You can buy them like this or you can just sew it into one you already own =) Memory Foam is good too but should also be set under or sewn into a saddle pad (you can buy them like this too.) Wintec makes very good therapeutic saddle pads, just make sure that you don't double up! Using two thick pads to protect your horse's back might be too much. You have to cinch the horse too tightly and that's uncomfortable for him. Because the saddle is perched on top of the thick pads, it might very well roll from side to side and not stay stationary in the middle of the horse's back. This, in turn, can cause a sore back.