Raising the speakers off the ground will improve the overall audio reproduction in your system. However, I can not see how the Harmonix Footers are an advantage given their size. In my opinion, they are too short to make a substantial difference and at $2,000 you should expect superb results from your purchase.
Decoupling the speakers from the floor is essential but you can do this with cinder blocks. Purchase them at any home improvement store and spray-paint them the same color as the YG's. Total cost @$25.00. The results are outstanding. Improved dynamics and fluidity throughout the system.
Remember that it's also necessary to raise the listening position by the same height as the cinder blocks.