Is it worth upgrading a Thorens TD125

To the best of my knowledge all SME arms take the same cut out, as do several other arms. I was an SME dealer in past years and in my experience all standard length SMEs will fit.

Here's a Hub thread you must have missed:

http://cgi.audiogon.com/cgi-bin/gallery.pl?blog&1260414740

Note that there's an Audiogon member named Chris who specializes in Thorens upgrades.

I wonder what differences are between the 125 and the 124 II which sells for a lot more and before the LP 12 was maybe with EMT and Garrand 301 the table to have (alright 70's had others like Mico Seki).The issue is is it one worth the refurbish/upgrade cost.Just a thought.
Chazz

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.