Audio Research REF 3 and REF 5 Tweaks

Hi,
I was wondering what tweaks have been used successfully with these two preamps? I'm thinking specifically of footers, weights, tube dampers, powercords, etc. I haven't considered tube rolling as from what I've read, the tubes ARC recommends are probably overall the best.

I've tried several products including Vibrapods/Vibracones, and various isolation products from Herbies on my REF 3 with mixed results. (I keep going back to stock.) So far the best tweak has been to purchase and place Herbies Ultrasonic Tube dampers on the two power tubes, the 6550 and the 6h30, in the powersupply. Strangely ARC does not include dampers for these two tubes but the addition of Herbies tube dampers really cleans things up.
I use Solidsteal shelving which have been damped with sand.
So what have you all tried that you think would be a worth whild audition?
Thanks in advance,
Sgr