Analog Novice concidering new tonearm, seeking rec

I am currently using a refurbished Thorens TD-160 with original Thorens Tonearm and Grado Silver MM Cartridge. Phonostage is a Space Tech Lab Vacuum Tube P-102, this feeding STL A-102 Headphone Amp with Grado RS-1 Headphones. Rumor has it that better performance can be had by replacing Thorens Tonearm with Rega RB-251 or RB-301. Expensive proposition, since cost of upgrade and installation cost more than used Turntable. Is there anyone with a Thorens Turntable that has tried this? What improvements in sound quality can be had with this Upgrade? Used Dealer offering $500.00 for Upgrade, is the cost/benefit ratio even worth it? I still kind of like the original Thorens Tonearm, and it is designed to match the original Turntable. Would it be worth my while to concider the Rega Upgrade?
Try searching on vinyl asylum, there are lots of Thorens owners there. I think the SME 3009 is a popular tonearm upgrade. A used Rega or Jelco is another possibility. Apart from letting go of your cash, I would not worry about the tonearm costing more than the table.
There's a couple Thorens 160's for sale on Vinyl Nirvana. One has a Rega mounted on it the other a Linn. You might want to talk to Dave and get his opinion as he refurbishes these tables.
Tried Vinyl Nirvana, Dave has a consulting fee payable via Credit Card, I guess. Don't have a Credit Card, don't believe in them. Just trying to get a feel as to weither improvement in sound quality would be worth the cost of installing a different Tonearm. Is it a small improvement or something more significant? How does one go about finding a Tonearm that is compatable with an old Turntable like the Thorens TD-160? Is the safest bet to keep the original Thorens Arm that was designed for this Turntable? Are there any Analog enthusiasts that are using old Thorens Turntables with different Tonearms with an significate, and successful increase in Sound Quality?
Is there anyone with a Thorens Turntable that has tried this?
I had one years ago. Had 2 in fact, one with a RB300 another with a SME 3009/2. I preferred the SME. Both arms are better than Thorens' own (which is OK, anyhow).
Go to & check out instructions on yr record player, there is a lot of info there.
It's a good TT, by the way; keep it.