Which "tweeks" are more important

Dedicated circuits. Two or three. One for digital gear. One for analog gear including amps, preamp and analog front end. Possibly a third for just the amp(s). Two should do the job. High quality brass outlets like Porter Ports offered here by Albertporter.

The best system sound results from squeaky clean power.

Being a certified tweekgeek, and definitely over the top I would recommend the power be your first focus. There are a number of things to consider, of course the power conditioner, but also dedicated line(s) for your system if possible, outlet quality, noise suppression on open outlets (Quiteline)to name a few.

I would look at racks and vibration after the power.

jd

I would go with power then isolation/vibration control for speakers, amps, the components.

Quality power conditioner first. I suggest, however, plugging your power conditioner into a dedicated outlet.