GW, answered your PM on this, but since you posted the question here, I'll copy my reply here too:
Hagen are not very good nor very accurate. LaMotte is probably the BEST hobbyist kit you can buy. You have to buy "professional kits" like Hach to get any better. Salifert kits are only a bit less quality than LaMotte. I have several LaMotte kits, and they are top of the line. Where most kits include a small spoon to measure out a dry reagent, LaMotte gives you a pill. NO chance of accidentally getting too much or too little. BUT, they are hella expensive to buy, and the refills cost about the same (or more) than the comparable Salifert kits.
I've been in the hobby for about 30 yrs, and for my money, Salifert is the best compromise between cost and quality. Personally, I wouldn't buy the crap they sell in the LFS. Just too innaccurate or undependable.