Is table really more importsnt than cartridge?

Rich, If you want practical, my sugestion would be that you do nothing at this point in time. Spend some time learning about turntable/arm/cartridge interface before you do anything or your likely to be flushing your $300 down the drain. You have to learn how to match the arm to the table and the cartridge to the arm and then match the cartridge to the phono preamp to maximize performance. Screw up one of these items and you're nowhere. FWIW, the place to start the process is with the turntable, otherwise you are building your house on sand (so the saying goes).

Thorens TD-320 is not ab bad TT. If you're looking to improve the detail and sound stage then I would suggest you replace the cartridge with MC cartridge like Audio Technica OC-9 or Sumiko Blue point Special (nude body so be very careful of installing this cartridge.)
Hope this helps. If you want to stick with MMs, the better Grado also good choice.
If I have to choose with a limited budget, I would definitely replace the cartridge first.

I think cartridge is much more important. I don't think I would be as brave as $2000 cart on a $200 table, but I would go as far as 2000/500 rather than 500/2000.

Winegasman,
First let me say that in the few "mismatched" rigs I've heard, the good table/cheap cartridge combination has always worked better than the other way around. So I agree with Sdcambell, Aroc, Albert Porter and Dirtyragamuffin. A better table/arm can do wonders for a modest cartridge. A topnotch cartridge seems to reveal the shortcomings of an inferior table or arm, IME.

For around $600-700 you might consider the Bix TT. I haven't heard one but I'd expect it to outplay a vintage Thorens. Just my $.01 to give you one option to think about.

P.S. to Skeyebox
I'm one of those nuts who cleans even new records before playing them. I don't just "feel" that it prevents damage, I know it does. YMMV of course, but my approach is also more prudent than your approach, so I'm stickin' to it when it comes to advising newbies. Are you really willing to shoulder some of the blame (and cost) if you're wrong?

The existence of used records in excellent condition is simply evidence that record cleaning is not a new idea. I've been doing it since the 1970's and others for longer. My favorite ebay sellers are disposing of private collections which were meticulously cared for. The junk I occasionally receive from other sellers sounds like it does due to a lack of care by previous owners.

BTW, please explain your distinction between "data" which you'd accept and "experiences" which you'd reject. I could ship you three or four Classic Records reissues that used to be dead silent. They aren't any more and probably never will be again, thanks to being played before being cleaned. Would those ruined LP's be data points or experiences? ;-)