I think you are understanding the situation correctly and there is no way round the 10 device limitation.
It is good that you have only one Apple ID. Whilst you can add match to up to 5 computers, it may be worth considering having at least one iTunes library that does not have match activated and manage music using home sharing. You can then manually sync with that library. Manual sync does not work whilst match is turned on.
Sorry for intruding in this somehow solved thread but I really would like to understand why then am I getting this message when trying to join iTunes Match with yet another computer.
"You have reached the limit of 5 authorised computers.
To subscribe to iTunes Match with this computer, deauthorise a computer and try again"
Aren't you saying that it would be possible to use 10? In fact I have only seven.
It seems to me that there is a diference between iTunes Match associated computers number and Itunes sore and so foutrh computers number.. Or is it a "downgraded version" for me living outside USA (even if I am paying the same as everybody else)?
This is in facto, too dificult.... Surely I am missing somethin...
" Authorizing and deauthorizing a computer allows you to manage which computers can sync or use apps, audiobooks, books, music, movies, or other content you've purchased from the iTunes Store.
You can use or sync your purchases from the iTunes Store on up to five different computers (these can be any mix of Macintosh or Windows-compatible computers). When you sync or play an item you've purchased, your computer is "authorized" for purchase using your Apple ID."
"vWhen you subscribe to or enable iTunes Match, your device or computer will be associated with your Apple ID. Your Apple ID can have up to 10 devices and computers (combined) associated with it. For more information about associating devices and computers to an Apple ID, see this article. "
And "see this article" here link directs us to:
"Your Apple ID can have up to 10 devices and computers (combined) associated with it. Each computer must also be authorized using the same Apple ID. Once a device or computer is associated with your Apple ID, you cannot associate that device or computer with another Apple ID for 90 days. "
What is then the "truth"? When I try to add another computer it seems (previous post) that the first is true (I only have 7 devices associated with my Apple ID). Not the second.