I own the Maestro, Oyaide R1, Synergistic Research tesla, Furutech GTX-R and the Hubble's mentioned in this thread. Each of these outlets do have there individual qualities.
But, there is a reason the Furutech GTX-R costs more ... its built better and sounds much better.
If your AC in the best you can get it, and your power cords are capable, the Furutech shines over the others.