I am assuming you want the cabinet to be part of the "kit". If that is the case try www.zalytron.com for a pretty good selection. Also, www.northcreekmusic.com If you want to try building your own enclosure that would mean a lot more choices.
www.gr-research.com - I have their Paradox 1. You also need to specify your budget, because "put together your own high end speaker" can mean lots of things to lots of people. The Paradox 1 kit, for instance, costs about $500/pr, and includes a cabinet, so all you do is solder/screw/sand/stain.