For most of us that use multiple head/preamp setups, we use a combination of rack units to acheive this. Most of the time, the power section of the heads are not used. A good power amp is usually utilized.
The items you will need are a switching system such as a bradshaw or DMC GCX, etc.. Also combined with that is a system mixer, such as a Bradshaw or DMC System mix. These are used not only to switch between heads, but to acheive a balanced volume between each head/preamp.
I personally use 4 different preamps and 3 different
power amps in my current rig. They are all routed through a pair of Bradshaw 4x4 Audio Controller, Bradshaw amp selector, and a pair of Bradshaw Line mixers.
You can also use the Digital Music Corp. GCX in combination with System Mix plus, which I use in my smaller rig.
All the info you will ever need on these items can be found here:
http://www.customaudioelectronics.com/
Or at Digital Music Corp's website here:
http://www.voodoolab.com/
(look under Ground Control)
Another excellent company is Axess Electronics
http://www.axess-electronics.com/
I hope this helps you.
