Help needed for isolation under the power amps

I need to circle back to putting the proper isolation and mass loading under my Conrad Johnson LP140 mono blocks as circumstances led to a poor resonance impasse: 

My active components (cfr my systems page) has space limitation due to the fact that they reside on two levels in the designated space of only 40"w x 28"h x 32"d within the custom made cherry cabinet that was designed for my AV needs in the mid 90s. On top of that, the cabinet has to be placed directly against the wall, which makes any change to the active components cumbersome. 

The cabinet stays (a compromise with my better half) so I can not have an audio rack where the energy drains properly to the (wooden) floor and unfortunately the European cherry of the cabinet resonates more than I would like. The "A/V equipment space" limits the use of more solid material underneath the amp (again, please see my systems page. Also note that I have Symposium Svelte shelves under the mono blocks which are not depicted as at that time when the pictures were taken as I trying them out under my other set of speakers).

Any suggestions, especially for under the mono blocks? I am going to raise the shelf a bit where the source components sits in order to put mass loading material under them. I can go as far as 4" in height.

So the question begs? Which material would you suggest? Under each amp, I could use e.g. a double stack of 16"x16"x2" pavestone, a duo of 18x12x3" granite surface plate machinist tool, may be custom cut marble slabs.   
Besides mass loading under the amps, I am thinking of adding some metal brackets between the cabinet and the back wall to offload energy as my wooden floor is a bit lively.

As for feet under the mono blocks I am currently using the BDR cones and pucks, hoping to change the frequency of the interacting resonance of the cherry wood. Am thinking to replace them with ebony footers once I have the proper mass load. Also here I solicit your suggestions for the footers.

Symposium would work and sound great.

Ebm, thanks but which one (Super Plus, Ultra?) As mentioned I have already Symposium Svelte Shelves under them. No mass loading?
Ultra is best.

Call Peter at Symposium, you can use roller blocks or fat pads. I use Svelte Plus with fat pads (4 ) under the amp and(3) under the preamp and roller blocks (3) under the tuner cd player and (4) under the turntable. (2) fat pads under a Nordost QB4 Symposium products seem to work and sometimes you can purchase B stock. Good luck.
Thanks ebm and polk432. I had the inclination to call Peter but I also needed advise if I should mass load beneath the amps.

I tried the Rollerblocks Jr and Rollerblocks Series 2+ with some degree of success before, having a feeling that the cherry cabinet resonates still a bit too much for my liking.

Maybe I should go composite, mixing various material layers - each conductive to vibrations as to pass on the energy - so that their conflicting resonance frequencies gets cancelled, hopefully yielding a nearly inert block.
Explain all of this to Pete, he won't steer you wrong.
For mass loading, nothing is better than the no-longer-made Bright Star Big Rock, a shallow (2-4", depending on model) sand filled box. I already sold mine, but they are out there somewhere! You can then use the Symposium products on top of the Big Rock.
As much as I hate to point this out, the sand box is 30 years old technology.  Mass loading and the sand were replaced about 20 years ago by real vibration isolation devices including one from the guy who sold the sand box but also Vibraplane, Seismic Sink, and many other mass-on-spring devices.
Symposium platforms use constrained layer damping and with a bit research you can clone the effect with materials more amenable to each component in your system for minimal expense. Even the ideas behind rollerblocks had a long diy thread on Hoffman forum.
Home Depot, large thick chunk of granite. On top of that a nice thick (3inch) cutting board, and tennis balls cut in halves. Works great, and inexpensive for my standards. 
Granite?I always thought granite rang like a bell?I like the Food Grade cutting boards.The combination of strips of hardwood all glued together  seems dead to any ringing or vibrations to my ears.
Are all the components on BDR shelves sitting on cabinet shelves ?

A 6" thick slab of granite that weighs 100 lbs won't ring.  You'll have to trust me on that one.
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Polished granite looks beautiful and I started off by mentioning that I was a.o. considering two 18x12x3" granite surface plate machinist tool (they are fugly but not that noticeable if they disappear somewhat under the amps). I intend to implement a "virtual earth" where upon "an energy diffuser" platform like the Symposium Svelte/Plus/Ultra will be put. The mono blocks can either sit directly on it or coupled through footers (depending on the budget and availability Symposium Rollerblocks HDSE, Rollerblock Series 2 or Stillpoints Ultra SS). 
A 100lbs wont ring but my back can't handle that anymore. The whole family has been put to the limit -noticed my pairs of not-so-featherlight-speaker sets ? Guess who helped them setup,,,- so I won't involve any of them helping me unless it is a matter of audio life and death. 

But I could also go the route w/o mass loading. Peter of Symposium suggests that may work. BTW Peter is a very helpful person, lightning fast email responses! I spoke only once to him several years ago and ended up with the Svelte Shelves and lots of footers. There are of course better ones like SRA but not in my budget range. 

I did more reading as I thought if resonance is the issue, why not see what speaker builders are using besides wood that is relatively cheap and easy to work with. Dupont Corian came up. Just sent off some requests on Ebay to inquire for 18"x18" plates custom made in black. I will try them at least for upstream equipment.

/Hew: I may consider DIY but like to stick with finished product for aesthetic and resale ease reasons. Definitely will try some DIY for the home theater system.
/samhar: please also see my system page. The mono blocks sit on Symposium Svelte Shelves with BDR cones/puck as footers directly onto the cabinet. The upstream equipment sit on a cabinet shelf, one indirectly through also a Symposium Svelte and a double stack of Rollerblock Series 3 (DAC), the other on a maple butcher block and Stillpoints Ultra SS (CDP).

Unlike most of you, where swapping out a cable, footer, even an isolation platform is easy, I have to disassemble everything in my "A/V niche" if I want to get anything near the mono blocks so trying out something under the mono blocks happens in reality once every blue moon and I use that opportunity to clean contacts, spray anti static stuff, check my BMI, etc.

Hence I need to ensure to have the best and most practical strategy possible.

So now we have a lot of great input, the larger question is: do I need to mass load under my amps? Should I haul two 60lbs granite slabs or some 18"x18" pavestones? Please vote now...
FYI The cabinet is relatively well put together and has a mass of at least 200lbs  (empty, estimated 350-400lbs with contents, I have removed stuff that "ring" during bass passages) but there is a drawer (not visible in my systems page) directly under the "A/V cavity" and I am not allowed to fill that one up with sand...arghh..

Keep your comments flowing...  
Thick cork & natural rubber.Like the IsolPads only bigger.

Mass loading via sand dates back far more than thirty years, to the 50's, when it was used in the huge bass reflex enclosures of loudspeakers such as Wharfedale, their large unbraced plywood panels resonating like crazy if not so damped. The British have in general disapproved of ml, feeling that mass merely absorbs vibration and releases it later in time, doing more harm than good. The Brits favour low mass/high rigidity structures, which moves the resonant frequency of objects higher, where (they feel) it does less harm. I mentioned the Bright Star Big Rock only because the OP asked for a "mass loaded material" to put under his amps.

Mass loading has definitely fallen out of fashion (including with myself!), but that's what he asked for! I would instead use an air bearing (the original Townshend Seismic Sink, or a DIY version thereof) for vertical isolation, coupled (no pun intended) with a set of roller bearings for lateral. A product like the Minus K would be even better, but at around $5k for a pair and far taller than 4", is probably unacceptable to jazzonthehudson!    

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/bdp24: As mentioned before, I am not sure about ml as Peter of Symposium hinted it may or it may not work. Before I trend to no ml, which is of course easier for me to execute, i.e. doing nothing.
So again, I am not asking for ml but I did ask for input and got your opinion, thanks!

Minus K is indeed not an option (did you try that out yourself?). I would rather jump on the more popular SRA boat before. Besides the fact that one CJ LP140 is too heavy for the Townshend Seismic Sink, it is meant for TT where isolation is key, not transfer of energy which is more important for power amps. 

Barring an eureka moment, I will likely circle back to Symposium and add Svelte Super Plus shelves under the mono blocks and try an additional layer (probably Dupont Corian) under the upstream devices.
Not yet on the Minus K, jazz, though I really want one for my table. At around $2500, it'll have to wait.
I LOVE Syposium. I did get some pretty incredible results with SRA, as well as still points.  Me - I'd get a divorce, have her take the resonating cabinet with her and buy yourself a nice rack that does what it is supposed to do for your components.  Married life is overated.  Can't hold a candle to good music. If you ever find your self missing her, just play some Julie London.  Once you hear her voice w/o that cabinet resonating, you will forget everythig ;-)
/cerrot: I wouldn’t gamble on the divorce as mostly one ends up with a trauma dealing with the lawyers and a residue of one's fortune, financial and emotion wise, that is in a worse case of matrimony. I count my blessings, my better half is indeed the better half. 
BTW you have nice systems! I haven’t tried Finite Elements yet.

Speaking with Peter yielded better understanding of isolation and the application of his indeed affordable products. He was very helpful!
I ordered some Svelte Plus under the amps and Segues for the upstream gear in my second system.  Thanks polk for the tip on B ware units!

A slab of 1 1/2 " granite is underway as well, just in case. I tried ml under the amp in the library as it also sits in a cabinet and it did change for the  better.