Well are you looking for something that contains all the parts, you just need to assemble it? Or do you want to build the cabinet as well? Bookshelves, towers? Price point for the kit?
I can certainly give some recommendations and advice, but if you want to browse around yourself then PE has some kits, but there's also
meniscusaudio.com
madisoundspeakerstore.com
diysoundgroup.com
Speaker kits, loudspeaker design services, sub-woofers and amplifiers.
Pi Speakers - unmatched quality and state-of-the-art performance
Selah Audio
As for cabinet design, all kits come with pretty detailed plans on exactly what you're supposed to do. However, the best resource for cabinet design help that I've found is PE Techtalk forum. Any questions or things you aren't sure about and they will get you set straight if I or someone else here can't help you. Still not a bad place to check out to see what project those guys are working on.
Tech Talk Forum