Anixter "Levels" is the program that eventually became the "Category" ratings used by the EIA/TIA (with the usual downscaling on the "category" numbers to the lowest common denominator). Anixter is the father of the "Category" rating system.
This is more than a marketing thing. When Anixter orders cable products (including information outlets, panels, connectors, etc), they order them by specification. EVERY incoming batch of cable is randomly tested in their Lab for specification compliance. If the cable doesn't meet the spec, the ENTIRE batch is returned.
Anixter works closely with their suppliers. The suppliers occasionally use the Anixter Structured Cabling Lab (and services) for new product developement and standards verification. The EIA/TIA has done testing in Anixter's SC Lab. They are truely one of the "Big Guys" when it comes to Structured Cabling.
I do not work for Anixter, I'm not a contractor, I'm not related to anyone that works there, but I've been to the Lab, I've seen the testing and the documents produced relating to SC testing. The people there are the best in the business.
When you get SC products from Anixter, you are GUARANTEED performance up to specification (when properly installed). The Lab is now engaged in doing similiar studies for Fiber Optic cabling.
That being said, keep in mind that thre are no current networking protocols that require more than Category five UTP. When you install to a spec that's greater than Cat five, you do so to cover possible future infrastructure applications. Also keep in mind, the the focus of structured cabling is not JUST LAN data. The cabling infrastructure may include components to carry anything from RF (Lucent has a BALUN for TV frequencies) to baseband video, to terminal emulation (3270, 5250, RS232, etc).
Jus' so ya know....
Scott