No, the way a Zapper works is not by how powerful it is, but by DC offset. Here is a qoute from Dr. Clark regarding this
"Subsequent testing showed it was not due to some unique design, or special wave form produced by the device. It was due to battery operation! Any positively offset [DC] frequency kills all bacteria, viruses and parasites simultaneously given sufficient voltage (5 to 10 volts), duration (seven minutes), and frequency (anything from 10 Hz to 500'000 Hz)."
It's a common mistake to think a more powerful Zapper is more effective, but in fact, the more powerful units are not Zappers! The $10 Zapper fits in Dr. Clark's criteria using 9 Volts and 23,000 Hz. The reason it is cheaper is not because of qaulity of results, but because it is a different design using CMOS curciutry which is faster to build and the parts are less expensive because they are smaller. I used the $10 Zapper to kill the mites my cat had, so it will work! but if you want a fancier Zapper you can get one from http://www.paradevices.com/
with dual frequency, but it's not necessarily going to do more for you! Talk to ParaZapper on here for more info about those!
I hope you find something. :)