Cheap tweak from Virtual Dynamics:

I plan to first try uniformly tightening the stock screws using the Wheeler Fat Wrench as demonstrated in the video. If that proves useful, then I'm going to look into the brass screws.

Tvad,
Sounds like a good idea. I don't have a Wheeler Fat Wrench, but I do have an older Black & Decker battery-powered driver that has similar adjustments. I recall that the video suggested starting at 8 ft.-lbs. torque. I think I'll do the same initially on the stock screws. I just came back from Lowe's and bought 3-packs of solid brass screws of the exact size of my speaker driver's screws. Each pack had six screws at $.98/pk.

I bought a Wheeler online from an outdoor sporting goods supplier. For some reason, I believe the equal torque on all the screws is as important as the brass screws. The screws are certainly the least expensive part of the overall tweak.

Of course, now you absolutely MUST have the screws cryo treated.

...just kidding.

I agree that the equal torqueing of the screws probably is as important as the composition of the screw.