Pro-Ject Extension 12 to SME Model 10

A better table is *very* important when upgrading. Some say most important, I just say a critical element of the 4 pieces ( table / arm / cart / cable ).
As to options, not sure what the SME 10 goes for but iirc around $6k with arm no? If so there are option both new and vintage worth researching ( SME does build fine tables but yes there are others).
Do you have any words about what you like about your vinyl experience and what you are less thrilled about? Might help suggestions...

I would assume an SME table would be better than any Project turntable.  I have no experience, just an opinion. 

Give this a read: its pretty rare to see tables compared that are so far apart in price but its pretty well written ( I have two out of the four tables myself ):http://zero-distortion.org/analog-shoot-anamighty-sound/

My suggestion would be to listen to it to help you make a decision. It would be very hard to determine whether to make the switch even based on the impressions of someone that has heard both. At a certain level of audio product, what's "better" becomes much more subjective.

I have not heard a SME Model 10, but I have listened to a well set up SME Model 30 for several hours. While I admired the sound quality for attributes that audiophiles care about (darkness of background, speed of transients, precision of its sound quality), it didn't move me. On the other hand, I loved the sound of a Rega Planar 10 set up in the same shop and in the same room. I would be happier having the Planar 10 than the SME Model 30. So I think you need to listen to the SME Model 10 to decide how you feel about it. The SME certainly seems to be built well, but that shouldn't be a deciding factor about a certain price point.