iTunes match limits you to 25,000 songs, but once you match you will find that many songs do not end up counting against your total. There is a very easy way to work around the limitation, however.
First, select a numb of songs that, when subtracted from your total, will bring that total unr 25,000. Get info on them and set the comments field to something like “unmatched”. Now, set the media type to podcast. This moves the files out of your “music” without deleting them, creating another library, or anything complicated.
Now, run iTunes match.