lowtempguru, you have some very impressive callers! I recognize the switch you are using seeing as I just received one in the mail today from RadioShack.
I like how you recommended other amplifiers. I can not believe that the RadioShack amp performs as well as it does when it is rated at 0.2w. How expensive are the two amplifiers that you recommended?
I also notice that you have used several different types of speakers/horns. Which one do you believe has performed the best? It would seem to me that the car speaker would offer a good response through low to high frequencies, but the horn style speakers would be louder.
Also, in your experience, what has been the most affordable wireless transmitter/receiver that you have purchased that performed well? It looks like you used a NADY in at least one of them, but that system is fairly expensive if I am remembering correctly.