It does not matter which computer you set up first as you can authorise both machines to play your music.
Once you have set up on one machine, the music will be available in cloud on second and available to download.
As you have a lot of pre 2009 music which will have DRM, most of your music can be upgrade to 256 Kbps purchased AAC - some wil not.
I'm going to slightly disagree with Jim on this and say iTunes Match is really not the most efficient way to accomplish what you want to do. See this KB article: http://support.apple.com/kb/HT4527?viewlocale=en_US&locale=en_US
Once you get the music files onto one computer, then I suggest you enable iTunes Match.