Synergistic Research HFT + FEQ

I heard this tweak at RMAF and brought it home on a 30-day free trial. Unfortunately it turned out to be a real system killer. I had 20 of the HFTs and tried them with and without the FEQ, using a ladder to put them up and take them down repeatedly. I couldn't believe how awful it was. Made it hard to enjoy my otherwise excellent ~$45k system.

I had a similar experience with their Quantum fuse. Never did trust anything with "Quantum" in the title. HiFi Tuning Supreme fuses, on the other hand, made my amps sound significantly better.