Thanks for the tip, had a kit with all "G" 1583 which sounded like your highest HFE rated q21 samples and socketed mine tonight and tried out the "F" 1583's and noticed the exact same changes. I don't have any low hfe rated ones yet but the difference is quite noticeable and in exactly the same way. I don't know how this is not audible to some however maybe they are on cheap computer speakers or have bad ears or something of that sort.
this might not affect some builds due to the variety of parts involved but on mine it was sweet.
TR-606, X0Xb0X, NanoZwerg, EMX1, Nord Rack2, Yusynth modular in progress, Ableton, Metric $*!t ton of plugins and counting.