You really only need a high quality test kit for the most important parameters, and the ones where the details count.
For ammonia, you should only have ammonia while you're cycling. Unless something awful happens, you'll never have ammonia again. Most people buy an ammonia test kit and only use it for a few weeks. Plus, your cycle isn't over until the ammonia kit reads 0, so whether it's sensitive or not really doesn't matter. If ammonia is there in any amount, your tank is not finished cycling. Same goes for nitrite. There really isn't a reason to spend a lot of money on ammonia or nitrite kits.
The test kits that are more important are nitrate, pH, alkalinity and calcium (if you have corals). And those are basically all you need. Some people test for magnesium, but most don't. Phosphate test kits of any brand are worthless and not worth buying at all. Not because they are bad test kits, but because algae will use all the phosphate out of the water, so it doesn't hang around in the water column, and doesn't show up on a test kit, even though you have a big phosphate problem.
LaMotte and Salifert are two of the best brands.
