Power conditioning for multiple dedicated circuits

I would definitely look for vendors and products that allow a trial and return period- I'm not suggesting power conditioners don't work- in fact, they may work effectively in eliminating more than what you intended. I eventually got rid of all power conditioning when I had my system set up in NY where I lived for a long time.
When I moved to Texas, I had a large (10kVA) iso transformer installed which feeds a sub panel dedicated to the audio system. The iso-unit, built by Controlled Power in Michigan, does have some surge protection and that is complemented by whole house surge protection.
I predict that we will get at least one suggestion that you only need one line and that all components (at least the analog ones) run from that with a distribution box- a power strip without switches, lights or other bells and whistles, or a power conditioner that functions as a distribution box. That was in my experience more common in the UK systems which typically didn't use the high powered amps often found in big systems here in the States. This may eliminate grounding differences among different power lines, but if you use fancy audiophile power cords, you will have to arrange the system and power cords to reach that single point of power.
I listened to the system in Texas for a while without the iso set up waiting for the transformer to be wired and built. During that time the two "ends" were connected with a junction box where the iso-transformer would eventually go. This so-called "dirty" power was actually pretty clean, which I attribute to newer infrastructure where I am (in Austin) compared to what I was used to in NY (deteriorated infrastructure). The system sounded a little bright to my ears at first, but it required a fair amount of dialing in. 
I can see instances where someone is in an apartment or is suffering from less than optimal power where a conditioner improves things. But, be able to return any unit you try if it turns out that something sounds lost in the process. A lot of the cheaper power conditioners act like filters and eliminate more than just noise--
 I don't normally put up  provocative posts-- and I don't intend this to be read as such, but just my experience. 

Take a look at the range of Audience power conditioners.  They have what you're looking for. And are sold by multiple dealers, some I'm sure with return policies.

@jea48 I did the 2nd scenario you described.  I chose this because when I went to Lowes to pick up the Romex they had a bundle of 12/3 wire that was 1/2 price due to a return.  Therefore each duplex receptacle has 2 hot, 1 neutral and 1 ground.  I removed the hot wire's tab and wired to a double pole 40amp breaker so they each have their shared 20amp breaker but you cannot forget to switch one side off in the event of later work.  I did not research nor ask about this method so the only reason was simplicity.  What are the disadvantages?  I originally thought about using 10ga wire but got swayed by the wire on sale.  From your response I suppose sharing the ground and neutral disqualifies them from being dedicated.  What is the disadvantage for they way I have them wired?  

I think you've now protected your 12 wire circuits with a 40A breaker, which is a huge mistake.
That being said, wait for jea48 to answer.