Is it worth upgrading a Thorens TD125

As an owner of a fully restored TD 125 MK II done by Chris Thornton, I would have to say YES!!!!!!!

This table is one of the best tables I have ever heard

What makes you think that a good stock TD125/SME3009 can't give you good bass, mids and treble?
Don't forget that what your asking for is also cartridge related, how well it's suited to the tonearm and how good the setup is not to mention the electronics and speakers.
I have TD124 MK 1 and 11's' and TD125 MK1 and 11's and frankly if someone ran a blind test using the same cartridge/arm on all of them I seriously doubt if I could tell you what table was being used.
Yeah, everybody wants a TD124, Garrard 301 or 401 but they aren't a guarantee to good sound, just good investments if they keep going up in price.
Others will argue that rim drive is the only way to go but my TD125's have plenty of PRAT and I think they are a huge bargain because the fad is rim drive right now.
And there will be the group that says you have to rewire the 3009 and replace the cable. All well and good BUT if your cartridge wants to see 300-500pf the old wiring may sound better if you have cleaned the connectors because the new wire and cable may have less total capacitance. Changing input resistance and/or capacitance has an impact on the response curve of MM and MI cartridges.

I should mention that I did "upgrade" my TD125's if you can call it an upgrade because it's really just fixing normal wear.
I have a new thrust plate or metal disc dropped into the bearing well for the end of the platter bearing to ride on and there's new oil.
All you have to do is drop the new metal disc into the bearing well and make sure it's laying flat then replace the platter.
Maybe $15 per table? I can't remember.
E-Mail Joel at j.boutreux@gmx.de and ask for the price of a thrust plate (metal disc) and oil for a TD125.
His English isn't fluent so do use all the terms like thrust plate, thrust bearing and round metal disc for the bearing well so he understands what you want.
You may hear a sharper and more focused presentation.

Sorry to bump an old thread but does anyone have any suggestions for replacement feet on a budget for a Thorens TD 125 Mark II? Any thoughts on other feet upgrades? I've seen some Thorens tables with isolation cone feet but was told those weren't really necessary as this is a suspended table.

I was hoping to keep the replacement feet under $60 if possible. With my Thorens TD 125 Mk II I'm currently using keyboard wrist rests with good results but I was looking for additional/better ideas.

Anyone have any experiences with trying different platter mats on the Thorens TD 125?

Thanks

I'd also suggest contacting Christopher at http://www.artisanfidelity.com these guys do wonders with the TD125. If you read into their descriptions they eliminate the old suspension and have new replacement motor and power supply options. The plinths they use for replacement are made from solid Maple (if memory serves me correctly).