OK,
It's easy to convert your K-2005 to a K-2006--but you have hunt up the K-1515-A or -C which is the FAS-DPD Chlorine test as a stand-alone single-test kit. Using that, instead of the DPD chlorine test in the K-2005, you'll have the same tests as the K-2006. The K-1515-A is about $26 from Taylor itself and the -C (which has more reagents) is quite a bit more--but is available at Amatoind.com for about $40. Considering the K-2006 is only about $48 from Amato Ind., it doesn't seem like much of a bargain.

Unfortunately, with the DPD kit, I don't believe you can dilute the sample the way you can with the OTO test to double, triple or quadruple the range of the scale on the test cell.