Top dog's are going to be Mettler Toledo, Rosemount and Hach for meters. Pretty expensive!
YSI, Hanna and Extech are in the reasonable range for a handheld meter. (under 1K) I personally would go with Hanna or Extech.
With the Titration method, I would still stick with LaMotte! Their methodology/technology is accurate enough to calibrate DO meters, but it has to be done correctly.
Hope I did not give you a headache.
Let us know what you come up with.
