Pro-Ject Extension 12 to SME Model 10

I am considering upgrading my turntable from a Pro-Ject Extension 12 to a SME Model 10.
Would this be a worth while upgrade?
Would it actually sound better?
Is there another turntable in the price range of the SME Model 10 to consider?
I am unfamiliar with the benefits of upgrading the turntable as this is the first that I have owned.
I would keep my current cartridge a Sumiko Pearwood Celebration II.
Any advice would be appreciated.
Thank You
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 ):
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.
Thank you for the responses.

The Pro-Ject Extension 12 is the companies first venture into making a higher end product which lists for $5000 and punches above its weight so to speak. It includes a 12" carbon fiber arm and it is sturdy as it weighs over 50 lbs.

I have been told that my turntable is the weak link in my system. My system consist of a Conrad Johnson ARTsa amplifier, Conrad Johnson ET7s2 for a Preamp, Audio Research Ref 2 se Phono Pre and Nola Grand Metro Reference Gold Speakers.

I find vinyl to have a much fuller sound with better low end grunt, separation of instruments, more detail, black space between instruments, better clarity in vocals and simply more pleasing to my ears.

Any suggestions on a turntable that would be an upgrade giving me more of the positive attributes that vinyl delivers?

The turn table does not have to be a SME. I would buy a used turntable as I can get better value.

Thank you for the advice.
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Pkelly1504, it will be very interesting to know why you plan upgrade have you found negative SQ in Xtension 12?

I have P-J RPM 9.1 and thinking my next upgrade: Xtension 12 or Signature 10.

The best recommendation I received are: Brinkmann (Brado, Osis), Clearaudio (Innovation, Ovation), VPI (Prime 21 and Signature).  But these cost a lot new, and need expensive dust cover.

Based on price point and top level X-line, Xt12 seems very high end, being weakest link in your system might be not valid I will investigate this if I ware you. It is possible need spend a lot money to get better sound from you already have..., not wise!

Also consider upgrading power plug from wall wart to box use detachable power cord, in case you haven't done that.

Also look for upgrading tonearm to better model (Breuer, Graham, Jelco are good example), tonearm can make significant improvement.

Good luck
@knight7m , You should upgrade your list with the Sota Nova Vacuum. It can also be had with a beautiful dust cover!
Agreed mijostyn5.
I like know what SQ differences between Sota and VPI.   I dont like tube sound, its moody and put me into sleep.   I like SS sound but similar to Krell: definations, resolution, extensions, neutral.
Having owned previously VPI TNT6HR and Technics SP10mkII, I now own and would agree on Sota. There a used ones out there because they've been around 30+yrs, they're HIGHLY upgradeable, and if SME was something you like, SME arms are one of the most common combos on the better Sota tables. 
FWIW, I had Nolas as my speaker when I owned the VPI & Technics tables. My system page details some of my impressions of the changes. Cheers,
I had a SME10 it is an excellent table and very well priced when you buy used, I used it with the SME M2-9 it was great match, you also can get a second armboard out of the UK so you can set up 2 arms, I moved to a Dr Feickert Blackbird that added a little better bottom end, recently have been using direct drive tables and like how the handle pace and rhythm compared to belt drives. The SME uses a sub platter under the main platter I feel that is a good design also has an outboard power supply. I have set up a couple of Project tables I don't think their build qulity is as good as other tables in the same price range YMMV
Dear @pkelly1504  : What is wrong with what you have today and what's what you are looking for? or maybe you are trying to change your front end because some  one :

""   I have been told that my turntable is the weak link in my system..""

All audio room/systems has weak links and each audiophiles opinions could be different about.

I never had the opportunity to listen that Project model and looking the other posts down the thread my advise is to follow @knight7m  that at least own/knows about the Project QP.

He said: change the tonearm .  I don't like 12" tonearms ( I assume it's what you own but maybe I'm wrong. ) that makes more harm to the cartridge signal that " all " the advantages by its proponents.

Now, your Sumiko cartridge was voiced by the designer mounted in a SME IV/V tonearm and this means that a very good match for it is a SME tonearm. This is an option for you instead to change the TT.

I will change a TT where I was aware of often speed unstability problems or that I'm aware of developed vibrations/resonances not well damped by the TT it self.

You are the owner of the ball and your call.

Regards and enjoy the MUSIC NOT DISTORTIONS,