I purchased X3 studio but am reconsidering.  I wonder if I can upgrade to Producer for the difference?  Anyone?

I should contact CW directly. the difference is well worth it though!

I figure the only difference is a lot more plug-ins are included.
 
Let's see...
XLN Audio Addictive Drums
AAS Lounge Lizard SONAR
AAS Strum Acoustic SONAR
Rapture (full version)
Dimension Pro
TruePianos Amber
 
QuadCurve EQ Zoom
BREVERB SONAR
Tape Emulator
Console Emulator
Tube Saturation
PC4K S-Type Bus Compressor
PC76 U-Type Compressor
TH2 Producer
PX-64 Percussion Strip
VX-64 Vocal Strip
TL-64 Tube Leveler
TS-64 Transient Shaper
Tone2 Bifilter2
Analog TrackBox
 
I you want any of the above and it's worth an additional $50 (which I think would be the price), then I would say, "yes."  Otherwise, there is no difference between the two (sans the above list, of course).
 
Kind regards,
 
Living Room Rocker