If you have little or no experience at building speakers, I would agree that the Louspeaker Design Cookbook is a good start, as is "Designing, Building and Testing Your Own Speaker System with Projects", by David Weems.
For (good!) free design software, and access to a speaker design forum, drop in at:
http://www.speakerworkshop.com/
Another excellent site is at:
http://www.diysubwoofers.org
Contrary to its name the focus is not only on subwoofers, and you'll find a lot of absolute gurus contributing to the discussion forum.
Scottmandue,
Trying to re-use old enclosures is not a good idea at all, as the enclosure is designed around the unique physical characteristics of a given set of loudspeakers.