I'm thinking about getting the Platinum upgrade and adding the MP3 Encoder, Rapture Pro, and TH3.
 
As far as the add-ons go, I consider the first one a must, because who doesn't need to encode MP3s?  But still debating on the other two.  I already have Guitar Rig, UAD-2, plus all of the effects included with the Spectrasonics instruments, and TONS of other instruments.  Yes, it's a 4,000 pound hard drive, and I need to use an engine hoist to move my laptop around.  It gets heavier with each new VSTi I add to it.  Man, that data is HEAVY!  [smile]
 
Opinions on Rapture Pro and TH3? 
 
Clarification:  I already have Platinum, my current subscription ends this month (I think), and it's the "lifetime updates" I'm thinking of buying.  My store page offers the other three things as add-ons.

The lifetime deal is a 'no brainer'. The Cake version of TH3 should give you an idea if you want to spring for the full version or not. I didn't buy Rapture Pro because I'm pretty happy with Rapture and Dimension Pro.
 
Rocky

I use rapture pro all the time.  I think its got some very usable attributes... sonically it has some great things.  My only pet peeve is that many of its patches are screaming loud..! HAHA!

Thank you both.  I'll think it over some more, but I'll probably get them all.

Yes to upgrade, no to TH3 if you have GuitarRig, and yes to RapPro. 
 
The Upgrade is, like said above, a no-brainer. Lifetime updates? Duh!
TH3: GuitarRig is the Rolls Royce of guitar emulators, so unless it's not working for you in some way I'd just stick with it.
RapPro: I've had some install probz with it but it's a great synth and if you can get it for the $39 upgrade price I've been seeing it's also a no-brainer. At that money you'd be crazy NOT to buy it. ;-)
 

TH3, as Bluzdog points out is built in to SPlat and will give you a really solid indication of what you can do with it.  I can't live without it, myself - its flexible, sounds great, easy to use, etc., etc.  I had the full TH2 before, though, so going to the full TH3 was easy and somewhat inexpensive.  I use GR 5 Pro for the effects, but don't bother with the amps and cabs - I just can't get the warmth and chunk from them like I do the Randall and Brunetti combos in TH3.  Great piece of gear though, that GR5.

You can easily set up the free LAME encoder to do mp3 export from Sonar if you need to. I never bothered as I prefer to render uncompressed and then use Sound Forge to encode whatever format I need. I know it's an extra step and unnecessary but old habits die hard, and I actually prefer it as it gives me another step in the process to catch potential errors. 

For encoder purposes, I've been using Pyro Audio Creator since 2012 and very happy with it. It actually does a whole lot more than encoding.......of course, it isn't free.  
 
https://www.cakewalk.com/Products/Audio-Creator/Convert

I bought the MP3 encoder and Sonar still won't save as MP3. I reached out to tech-support we'll see what happens.

Got busy with other stuff but now I'm back and looking at this again.  The addition of all three add-ons raises my upgrade price to over $430.  I'm feeling a little whiny about that.
 
I'm thinking of leaving TH3 off of the order.