I also have a memory foam topper, and it's wonderful. More than worth what it cost.
Using extra pillows is also a very good idea...... I suggest to people that they experiment to find out where and what kind and how many. I sleep with several pillows of different sizes and shapes and use them during the night in different ways.
Since sleep is SO important, for everyone but especially for us, I think any expense is justifiable if it provides better sleep. I encourage all of us with fibro to budget and save for it, but to spend what it costs to get exactly the kind of sheets you like the best, the pillows that work for you, the topper or mattress that works, if at all possible. If you really cannot afford what you love the most (my favorite pillows in the world, for instance, cost $300 each so that is not happening), then at least get the best you can.