Power wiring for amp + stompbox "preamp" modules

[therecordingart]

This was also posted at SSGuitar.

I'm showing my noob here, but what is the best way to wire up power for the power amp circuit plus a lower voltage "tap" (excuse my use of the word) for the preamp modules.

-Wire a 9v regulator in parallel with the power amp using the DC coming from the rectifier?

-Wire a 9v PSU in parallel with the rectifier using the AC coming out of the transformer?

-Wire a separate transformer in parallel to the other transformer using the AC from the inlet?

I apologize in advance if this is a dumb question, and your help is greatly appreciated.

[defaced]

They all will work, the issue is ground, or rather voltage referencing one side of the voltage rails.  All of this discussion depends on the dirty details of how these two parts connect and such.  You really have to look at this from a "system" standpoint, not a "component" or "device" standpoint, which is why grounding is important. 

In the first example, the "negative" rail is common between both power supplies.  This may introduce ground loops when you plug the preamp into the power amp

In the second example, the "negative" rail of the 9v supply is floating.  This could present a safety issue because now you have one device with a floating power supply, but it could also solve possible ground loops.

In the third example, both supplies are completely in parallel and completely isolated.  This would be the "best" way to do this because both power supplies are isolated by the two transformers - this is how I would do it.  The only issue I could possibly see is if the chassis have to be connected between the two, then things will get sticky and possible ground loops could be created.