To follow up on the B&M shifter and the humming/rattle at high rpms, it appears that PDM racing has the newer ones just by looking at the box.
http://www.pdm-racing.com/products/drivetrain.html
The box that mine came in was different than this one. I'm assuming that this means these will be the newer version with the improved dampening.
And as for shift knobs, I have the Nismo leather knob which feels nice, but I don't see why the knob would matter as to the noise.