Blue Jeans Cable assembles Cat 5e, 6 and 6a using Belden cable to the length you need but more importantly, each cable is individually tested using a Fluke meter to ensure it meets spec and you receive the report. MeiCord Opal UTP Cat 6 as also garnered great reviews. Or Ghent Audio, who assembles Cat 6a using Belden stock with Metz shielded plugs, perhaps worth a look.
