Here's an update on the Sonar upgrade path.
http://blog.cakewalk.com/cakewalk-announces-simpler-sonar-prices/#more-25515
 
Starting May 1, 2017, if you want to upgrade your copy of SONAR to a more advanced edition, you simply pay the difference in the current price.
 
If you own SONAR Home Studio, upgrade to SONAR Artist, Professional or Platinum for $49.99 off the regular price.
If you own SONAR Artist, upgrade to SONAR Professional or Platinum for $99.99 off the regular price.
If you own SONAR Professional, upgrade to SONAR Platinum for $199.99 off the regular price.
 
You may want to log into your Cakewalk account before May 1st, to see if you are currently eligible for an upgrade price from X3 Studio.  Any available X3 upgrade paths will expire when the new pricing plan goes into effect.
 

Hey guys.  Yep went from MC which was the first thing i bought and went to X3.
 
Hi Ab...  I'll log in there and see if I still qualify for upgrade price.   So Artist would be next up and then Professional after that?   

I can't upgrade anymore. My subscription expired. Not sure of the monthly option still exists.

I kept X3 for a looooong while, but finally upgraded when X3 showed itself unworthy of recording/editing the sustain pedal when I was playing piano.
 
My advice is to go for Artist. For someone in your position, you might not need the extensive bloat that comes with Producer. I have Artist, which I think I bought outright for $79 a few years ago. I have never upgraded it from my original purchase, and it still works great.
 
If you go with Artist, you then have to pony up some for the cool VST plugins, but you can pick and choose those that suit your liking. Another idea is to add Kontakt as soon as you can, there are a ton of libraries out there that are just brilliant.
 
I'll admit being utterly confused as to the current Cakewalk purchasing/upgrading systems. If you can still just buy a piece of software and use it, then I'd do that.
 
best of luck!
-Tom

It's 40 per month or 420 straight out a saving of 60. So under current curcumstances it might just go for the monthly.

Agentcalm
Hey guys.  Yep went from MC which was the first thing i bought and went to X3.
 
Hi Ab...  I'll log in there and see if I still qualify for upgrade price.   So Artist would be next up and then Professional after that?   

I'm not sure what came with X3 Studio, but if that was a step up from MC, then you probably want to look at Artist or above for unlimited tracks. This appears to be the only cut down core feature in HS as compared to Artist.
 
If you are interested in using ProChannel modules and the new patch points and aux tracks, then Professional and above would be recommended.  Professional also includes the Mixing and Engineering Suites. Plus more instruments.
 
I assume that Cakewalk basically morphed MC into the new Home Studio.  So even if you just went with HS you could still use the plugins that came with X3 and get an updated Sonar core software in HS.  That is maybe all that you need for songwriting, if 64 tracks is enough.  You mentioned Session Drummer3, which you already have.
 
You will get the same core Sonar interface, with the same recording and editing functions in any version.  Other than the few core features mentioned above, the main difference between the current versions is the included plugin bundles, which is really what you are paying extra for. 

Download the current demo and try it, then decide whether to upgrade and if so to which version based on what you find you need/want to be able to do. If you don't need the 'comes with everything' version then don't pay for it if you don't want to or don't need the extras over the version that meets your needs.

Hey guys.  some great tips there.  Tom , Artist might be all I need to be sure. I dont use the pro channels and can use stock EQ, compressor etc. 
Ab did mention that Professional has mixing and engineering suites so they might be worth looking at.  
Yep i agree that a monthly payment would be less painful than forking out full whack in one go.
Kontakt was mentioned earlier.  I dont know what that is but Im heading straight to Google it now.  

Agentcalm
Hey guys.  some great tips there.  Tom , Artist might be all I need to be sure. I dont use the pro channels and can use stock EQ, compressor etc. 
Ab did mention that Professional has mixing and engineering suites so they might be worth looking at.  
Yep i agree that a monthly payment would be less painful than forking out full whack in one go.
Kontakt was mentioned earlier.  I dont know what that is but Im heading straight to Google it now.  

Take another look at the feature comparison page.  The "mixing and engineering suites" is just a fancy way of marketing more EQ's and compressors, etc.