I have the PPI pcx 4125 Isaac and personally I have never had a ny problems with it and it sounds great. I am running 2 sets of boston acoustic pro 5.25 component sets with it and it is doing its job flawlessly. But thats my opinion I guess. James
For PPI, the only amps they ever made that I drool over are the older Art series models. The Orion HCCA is a great amp, but only if you can run it at 1 ohm stereo or 2 ohms bridged. Otherwise it's wasted since it's designed to run best at low loads. The Zapco is a fantastic amplifier. The Studio line is an older amp, but still built with precision and care. Really it's a matter of matching the amp to what you need it for. between the three if I was given the option to take one for free, just on personal preference, I'd take the zapco amplifier, then the orion.
Thanks for the input. PPI was my 1st choice till I saw Orion HCCA, then I saw Zapco and it blew away PPI's spec. I can see why you like Zapco products so much.