Support table or shelf for turntable

I guess the pursuit of audio satisfaction can be stressful (time and money). It often leads to disappointment and desperation.

The great thing about forums is that we know we are not suffering alone. We can even begin to laugh together.

I'd be the first to admit that I spent decades ignoring good advice, and I'm probably still doing it.

At least I can take consolation in knowing that I can enjoy all my 3 systems. From the full on Tannoy Berkeley's, Rega RS1s, JVC tube/wood cone speaker mini system and last but certainly not least, my Sony CMT-CQ1 micro. 

Not everyone's cup of tea but my best attempt to extract max tonal density from HiFi. That's the key I think, knowing what pushes all the buttons in your head.

Its a labour of love, and love is a strange thing.

Whoa! Hey, leave me out of your petty disputes. Note to self - A biology major thinks I’m weird. That’s weird in itself.

@noromance props for the Quads. Have owned my pair, recently restored, since 1973.
I had a plinth like yours that was custom made in 1973 for my then new SP-10 turntable by Mel Shilling, an old time Philly audiophile who ran a shop called Music & Sound. Thing rang like a wooden bell. I kept it at a remove from the speakers, behind an alcove wall and used no special audio furniture or isolation devices at the time--there really wasn’t as much available to audiophiles though savvy DIY types may have known more. One aspect of the Quad is the dipole radiation pattern, so though your table is behind the speakers, it’s getting acoustics waves from the back of the speaker.
As to isolation, I’ve had issues with the last two houses I’ve owned, both restored, period houses with wooden floors. I was able, in the NY system, to mass load a very heavy mahogany prayer table by using chunks of sorbothane under the table legs; on top of that sat the table and HRS platform for it, which weighs 231 lbs. The prayer table was probably a couple hundred pounds. I still had footfall issues, but the table was outside of the line of fire of the speakers, in what amounted to a large,room-sized alcove.
In my new "old" place in Texas, i had a structural engineer visit for other reasons, and asked him to tell me if there was some way to wall mount 231 lbs worth of table. He didn’t care so much about the weight or mass of the table, but said the way the house was built-- all wood, including wood slat walls, they were moving, and not a secure mounting point to eliminate vibration and footfalls. I wound up buying a big Minus K. Not a bargain, but it made me a believer. There is another company that produces similar isolation devices as components- Newport?, apart from the usual suspects like Vibraplane, Herzan, etc.
One possibility -- if you change the plinth before investing in any spendy isolation products, and get the turntable out of the line of fire of the speaker forward or rear wave, you may escape without additional cost.

Good stuff whart. All my speakers are dipoles (original Quads, Magneplanars, Eminent Technology LFT's), and I have been dealing with their backwave for years. But imo that wave is of less concern that is the vibration coming up into a turntable from below, the very low frequencies. That is true even if the table is not just out-of-line with the speaker sound, but even in a different room from them. A Minus K is on my to-buy list!