Yes, the Taylor kit is best. The AquaCheck test is cheaper and easier, but isn't very useful at PO4 levels above 500 (0.5 ppm). Water company samples may have 4,000 ppb (4 ppm).

You'll find the Taylor kit info toward the bottom of this page: http://pool9.net/tk/

PS. Even with the Taylor kit, you may have to dilute samples. If you do, buy a gallon of DISTILLED water from Walmart., to dilute with.