Hi Speakersound. Have you visited your neighbour to see (hear) how bad the problem is? I lived in an Edwardian flat, so at least I did have sound proofing (ash) between me and my downstairs neighbour. When I first moved in I had my speakers on two wooden units and they acted like boomboxes. When I did get speaker stands there was an improvement in SQ, particularly with the bass which tightened up and became brighter, which is how I like it.
They were Atacama stands made out of metal, filled with sand in the poly bags provided, spiked on the base and speaker blue tac'd to the top.
When I asked my neighbour she admitted that she rarely heard anything and if anything felt I was being disturbed by her TV, which I was not. After that I cranked up the volume a bit more!
So my advice is to get speaker stands anyway just to improve sound quality and go and have a chat to your neighbour to see how loud you can go.
I now have a headphone system only and if you do find that you have issues with your neighbours, headphones will make them go away.