Seriously, if you go with concrete blocks your choices are between dense and lightweight. Dense are a bit less likely to tip or crack but are harder work to transport. You may want to stabilise the dusty surfaces with a layer or two of cheap quick-dry paint. If you pile up more than one then thin carpet underlay between them may make the structure more stable and give you some sound isolation from the floor. Obviously laying them on their side allows you to change the height in increments of a little over 100mm.