I've been using Home Studio 9 for 13 years on Windows XP, strictly to edit midi files from outside sources.  I use these files as accompaniments for group and choral singing.  With XP about to be extinct I'll need to upgrade to Windows 8 I imagine, which would mean upgrading Cakewalk as well.  What Cakewalk product would be similar enough to Home Studio 9 that the learning curve wouldn't be too steep?  I'm very adept at Home Studio 9 screens for midi editing and would hate to have to learn a whole new method.  What do you suggest?

As far as I have noticed Sonars MIDI editing has stayed about the same over the years. 
You would probably be happy with X1 LE which comes free with most Roland keyboards and audio interfaces. Not sure what it costs alone $49? . Go to the top of the forum and look them up under Cakewalk products.  

http://www.store.cakewalk.com/b2cus/ProductInfo.aspx?productid=10-X1G31.00-20E
 
Thats $59  for X1 LE
 
So a much better deal for you, if your version is registered with Cakewalk is this one for $49
X3 a  way more powerful version and X3 is the best version so far. X1 was a little buggy.. 
As far as I can tell Cakewalk does not make the old Home Studio series anymore. 
 
http://www.store.cakewalk.com/b2cus/ProductInfo.aspx?productid=10-CXSR3.00-30E
 
There's also Music Creator which I no zip about, but it does midi and is only $20
http://www.store.cakewalk.com/b2cus/category.aspx?categoryID=58&cat=58
 
 
 

There are two choices:
The least expensive solution is Music Creator 6 Touch. It is based on SONAR X2 with track and plug-in limits. See here for the limitations on the software.
The other solution is SONAR X3
 
MIDI editing is essentially the same in both of the products.

And both are somewhat different than HS9. No matter what you get there will be a learning curve. Read the forums for tips but download the help files and/or videos and take time to learn the ropes. You'll be miles ahead and avoid hours of frustration.
 
Steve