The urge to tinker is awash. What TT might better mine and why?

I  have had the GL 99 modified as you can upgrade the idler and bits more than you can the GL75. I certainly think you will not buy a pig in a poke with a good condition GL99 and 479$ in the above advert is a steal if in good nick. I paid £500 for mine but it was refurbished in all super finishes and looks perfect /new

As the owner of a much modified Lenco and four high quality DD turntables, and having owned a Notts Hyperspace before embarking on my odyssey with idler- and direct-drive, I feel confident in saying that any top notch vintage DD or any well developed Lenco or Garrard will certainly sound "different" from what you've got and in my opinion, better.  You keep asking "why", but most of the why is built into your own preferences, so it's hard to say why.  I can only say for myself that the idler and DD options produce music that is more like real.  You can read the cliches about rhythm and pitch elsewhere.

@lewm 

Thank you and I guess I should explain what I mean by "why".
Not asking why will it sound better but why might the technology of a different TT help better the SQ of my present TT.

And yes I fully realise it is all still down to personal preference but with prices of TT running many thousands above mine I am genuinely curious.

You mention dd, something like Denon DP 3000 or similar?

Belts are elastic. Stylus drag is real. ;-)

So are we saying that DD and idler drive maybe better tech than belt drive?