I currently am running X3e Producer.  If I upgrade to Sonar Artist, will I be able to use the prochannel and prochannel plugins that I currently have?  Or will it be unavailable since prochannel isn't included with Sonar Artist?  I mainly want the bug fixes and workflow enhancements. . . I already have lots of plugins.

No, PC plugins will not be available at all in Sonar Artist UNLESS you bought the PC plugin which also included a VST version.  but Artist version will not have Pro Channel shown, so you can't insert any of the PC plugins.

I thunk this has been answered before but for the life of me I don't recall what the answer is.
 
{quietly slips out the back door}

OK so sounds like I'd have to go with Professional at a minimum, and at that point I'd be foolish to not just get Platinum and get the extra Addictive Drum packs for $50.  I'll probably stay with X3 for a while since it's very stable.  But I am interested in the workflow enhancements in the new Sonar!

Actually I'd like to raise another question after more thought.  Like I said, I have X3E Professional and it works well, but I would like to upgrade to the new Sonar to get continued bug fixes as well as the improvements to workflow.    However, I don't want to lose what I currently have with the prochannel and the fly-out EQ.
 
I really don't want to shell out $150 for Platinum, as I have no use for vocalsync, drum replacer, etc.  Even moreso, I don't want to get into shelling out $200 a year after that for additional features that I probably won't use.
 
Anyone have a suggestion?

Keep what you've got.  If they release a feature that you think you'll love then jump in at that point with a one off lump sum $200 and call it an upgrade.  You'll get all the upgrades up to the point you buy in (excluding any short-term offers that may have expired) plus another years worth of upgrades.  It's effectively a 2 for 1 offer.
 
At the end of the 12 months you don't have to pay again if you don't want to. You could wait another year or more then jump back in again....

Thanks Karyn, you are right. . . . that does sound like the best approach.  Bummer that I have to wait for the bug fixes and feature enhancements, but X3e works pretty darn well so I can live.
 
By the way, does Platinum include the tool to export MP3 files?  Or would I still need to pay the extra $10?