Would an Isolation TT platform further improve my TT?

I will look into the Segue ISO. Looks interesting. My TT is 55 lbs. so the medium platform would cost $549.

Symposium discovers springs. Whoa! Shut my mouth and call me corn pone!

Thoughts on the Vibraplane? I think it’s still considered the gold standard. Yes expensive at $2500 but less expensive than other item. 

@rsf507 - You gets what you pays for

Vibraplane ELpF 95% at 10Hz - and a rather pronounced bump at its natural frequency of appx 2Hz - $2.5K plus compressor

Minus-K CT-1 99%+ at 10Hz (vertical), 95% or so (horizontal), natural frequency vertical 0.5Hz (good) but horizontal 2.25Hz (not so good) - $5K

Herzan TS-140 99% at 10Hz in all 6 axes, 90% at 3.5Hz, natural frequency <0.5Hz - $10K

In others words the extra money goes to dealing with 3-10 Hz and in more degrees of freedom. As 3-10Hz is where seismic activity is (pace Townshend et al) I’d at least go with the Minus-K as this is the sweet spot for performance vs price and on a rigid stand which isolates form horizontal transmission (i.e. translates seismic activity into mostly up-down) should perform well. Plus the Minus-K is completely passive.

Also adding seismic isolation will also potentially change the sound of the table

As @noromance noted 

I have always found that the more rigid the support, the tighter, more incisive and clearer the sound

The same is true for true seismic isolation -- you will get an even more clear, direct, un filtered and accurate presentation of the LP. Frankly what this means is that a lot of what many people like about analog ("warmth", "bloom", "space") is sharply diminished - if it's not present in the recording.

The reason is is because a lot of these apparently positive benefits are colorations from external vibration and taking it out at first listen can be shock -- LPs sound a lot more like digital in that regard after isolation. But the plus side is unparalleled L-R clarity, greater tonal variety, better micro dynamics and all around an ability to more closely engage with the disc. This really pays back on classical but if your taste runs to rock you may prefer the "before" result ... I've been able to do this test many times with my Herzan as you can switch it in and out and a fair minority of listeners prefer the sound without it on