Ok here is my Question...I have Sonar 8.5 Producer and want to upgrade to X3...Now I have the full version of Dimension Pro and Rapture that I got with producer....Lookng at he X3 upgrades, the Producer edition comes with that also for $199 and the Studio does not for $99..Question is since I bought the 8.5 producer and already have it...can I just upgrade to X3 studio for $99 instead of paying for it again???

The upgrade to X3 Studio from any version of SONAR is only $99.  It wouldn't matter if you had X2 Producer or SONAR 8.5 Essential.

Why not go to the Cakewalk website and check the comparison features between the various X3 versions, then you can decide as there's more between versions than the synths you mentioned

No... I have sonar producer 8.5 with dimension pro and everything else and i bought x3 studio because i had the other stuff and after install and vst scan, there it was, in fact i used dimension pro today on a project, but you may want to consider x3 producer for the other things it comes with... i am already thinking about going up to producer myself.
sonar x3 studio is a blast to work with, very stable, not perfect but still really stable
Michayl

Thanks Michayl thats the info I needed..I don't need all the extras of producers..I also have Reason and Maschine and just ordered Komplete 9 ultimate....I just need to use SONAR as a host DAW so I can run all 3 at the same time. SONAR 8.5 doesnt have 64bit rewire support and that was the main thing I wanted.

To the best of my tiny little brain, after reviewing the differences between Studio and Producer versions of X3, I think you are correct about not needing to spend extra, however, it might be worth spending the extra $50 now, as you would also have a gap in FUTURE upgrade versions, and only you can additionally determine if the other differences (listed below), would be things you would miss.
 
Here is the Cakewalk link showing features comparatives between the X3 versions:
 
http://www.cakewalk.com/products/sonar/versions.aspx#Instruments
 
From the above, and considering you already have Dimension Pro and Rapture, the following seems to be what you would not be getting:
 
Z3TA+ Classic
XLN Audio Addictive Drums
AAS Lounge Lizard SONAR
AAS Strum Acoustic SONAR
TruePianos Amber
 
BREVERB SONAR
Tape Emulator
Console Emulator
QuadCurve EQ (Zoom)
Tube Saturation
PC4K S-Type Bus Compressor
PC76 U-Type Compressor
 
TH2 Producer 
BREVERB SONAR
PX-64 Percussion Strip
VX-64 Vocal Strip
TL-64 Tube Leveler
TS-64 Transient Shaper
Tone2 Bifilter2
Analog TrackBox
 
Again, there are also likely to be additional things in future upgrades, like someday X4 or whatever it might be called, and you would have to consider a likely upgrade difference at that point too - meaning probably another $50 difference at that point, balanced against whatever comes with that new version.
 
If you instead bit the $50 now, you would never have to worry about that for the future.
 
Bob Bone
 

One thing to remember is....if you do decide to just upgrade to Studio...do not delete your 8.5 version or you may loose your Dim Pro and Rapture.  Though you could probably do a custom install of 8.5 and reinstall just those things.  I never owned 8.5 but I assume you can do custom installs with it too.
 
But for the extra $...it's well worth all the extra stuff you get with X3 Pro.

The uninstall process asks if it can delete dll's, and if you say 'No to All' those should not get deleted.  (referring to the plugins from 8.5.3).
 
You WILL lose V-Vocal though, as it was replaced in X3 by Melodyne, if you delete 8.5.3 and do not have X1 or X2 present on your computer.  V-Vocal is part of the base install, so you may want to consider that - though I personally prefer Melodyne over V-Vocal.
 
Bob Bone
 

I do recommend that you splurge the extra $50 to get X3 Producer.  Even if you do not think you will use some of those added features, you may end up changing your mind downstream, and once you are into the Producer level of any version, you will always have the cheapest upgrades to the most features for future upgrades.
 
I believe you would be very happy with the Producer version.
 
Bob Bone