Okay, well the first thing is that the latest version of Jaikoz 5.4.0 has a couple of fixes for AcoustId matching that the current version of SongKong does not have, so if you have Jaikoz try running your unmatched songs through Jaikoz, although remember you’ll not be able to load all 90,000 songs in one into Jaikoz. You read more about this at http://jaikoz.blogspot.co.uk/2013/06/better-acoustid-matching-in-jaikoz-540.html
I’m currently working on a new version of SongKong that will incorporate this and a number of other fixes.
Secondly, of course Jaikoz cannot match to MusicBrainz if the songs do not exist in MusicBrainz. MusicBrainz relies mainly on manual entering of releases from users, but they are in the process of making things a bit easier
http://geordi.musicbrainz.org/ contains datasets of data that may not be in MusicBrainz and allows you to prepopulate the MusicBrainz editor with data from these releases (similar to how Jaikoz lets you add a release from your own data). It currently contains all the releases in Discoga and Wcd. The plan is to start getting datafiles directly from Record Companies which will really help.
Geordi is not yet finished, but I find it works quite well if you have an artist currently not in MusicBrainz, then you can add all their releases from Discogs without worrying you are going to add a release already in MusicBrainz.