Where you been hiding under a rock???
PPI, Precision Power Industries. Been around for a very very long time. The ART series and the PRO MOS series are some of the best "old school" amps around. Very good, solid clean amps. The PC series is their later line and they are generally regarded and being good amps as well. I have a pair of PC2600's myself and they are excellent amps and have been utterly reliable. Any of the white ART series or black or white AM series are very good. The do get a little pricey cause peeps know quality when they see it..