Which "tweeks" are more important

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.